Liberty Property Limited Partnership 10-Q 3 Aug 17 2017 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information Document - shares	6 Months Ended
	Jun. 30, 2017	Jul. 31, 2017
Entity Information [Line Items]
Entity Registrant Name	LIBERTY PROPERTY TRUST
Entity Central Index Key	921,112
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Jun. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q2
Amendment Flag	false
Entity Common Stock, Shares Outstanding		147,317,203
Liberty Property Limited Partnership [Member]
Entity Information [Line Items]
Entity Registrant Name	LIBERTY PROPERTY LIMITED PARTNERSHIP
Entity Central Index Key	921,113

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Real Estate [Abstract]
Land and land improvements	$ 1,094,121	$ 1,094,470
Building and improvements	4,562,908	4,501,921
Less accumulated depreciation	(995,032)	(940,115)
Operating real estate	4,661,997	4,656,276
Development in progress	410,027	267,450
Land held for development	351,933	336,569
Net real estate	5,423,957	5,260,295
Cash and cash equivalents	14,748	43,642
Restricted cash	18,115	12,383
Accounts receivable	14,509	13,994
Deferred rent receivable	120,124	109,245
Deferred financing and leasing costs, net of accumulated amortization (June 30, 2017, $161,544; December 31, 2016, $152,309)	159,112	153,393
Investments in and advances to unconsolidated joint ventures	268,346	245,078
Assets held for sale	2,731	4,548
Prepaid expenses and other assets	137,993	150,235
Total assets	6,159,635	5,992,813
LIABILITIES
Mortgage loans	271,851	276,650
Unsecured notes	2,281,650	2,280,286
Credit facility	177,000	0
Accounts payable	56,188	65,914
Accrued interest	21,718	21,878
Dividend and distributions payable	60,334	71,501
Other liabilities	222,697	206,124
Total liabilities	3,091,438	2,922,353
Noncontrolling interest - operating partnership - 301,483 preferred units outstanding as of June 30, 2017 and December 31, 2016	7,537	7,537
EQUITY
Common shares of beneficial interest, $.001 par value, 283,987,000 shares authorized; 147,304,661 and 146,993,018 shares issued and outstanding as of June 30, 2017 and December 31, 2016, respectively	147	147
Additional paid-in capital	3,666,703	3,655,910
Accumulated other comprehensive loss	(45,332)	(56,031)
Distributions in excess of net income	(619,929)	(596,635)
Total Liberty Property Trust shareholders' equity	3,001,589	3,003,391
Noncontrolling interest - operating partnership
Noncontrolling interest - operating partnerships	54,170	54,631
Noncontrolling interest - consolidated joint ventures	4,901	4,901
Total owners' equity	3,060,660	3,062,923
Total liabilities, noncontrolling interest - operating partnership and equity	6,159,635	5,992,813
Liberty Property Limited Partnership [Member]
Real Estate [Abstract]
Land and land improvements	1,094,121	1,094,470
Building and improvements	4,562,908	4,501,921
Less accumulated depreciation	(995,032)	(940,115)
Operating real estate	4,661,997	4,656,276
Development in progress	410,027	267,450
Land held for development	351,933	336,569
Net real estate	5,423,957	5,260,295
Cash and cash equivalents	14,748	43,642
Restricted cash	18,115	12,383
Accounts receivable	14,509	13,994
Deferred rent receivable	120,124	109,245
Deferred financing and leasing costs, net of accumulated amortization (June 30, 2017, $161,544; December 31, 2016, $152,309)	159,112	153,393
Investments in and advances to unconsolidated joint ventures	268,346	245,078
Assets held for sale	2,731	4,548
Prepaid expenses and other assets	137,993	150,235
Total assets	6,159,635	5,992,813
LIABILITIES
Mortgage loans	271,851	276,650
Unsecured notes	2,281,650	2,280,286
Credit facility	177,000	0
Accounts payable	56,188	65,914
Accrued interest	21,718	21,878
Dividend and distributions payable	60,334	71,501
Other liabilities	222,697	206,124
Total liabilities	3,091,438	2,922,353
Noncontrolling interest - operating partnership - 301,483 preferred units outstanding as of June 30, 2017 and December 31, 2016	7,537	7,537
EQUITY
General partner’s equity - 147,304,661 and 146,993,018 common units outstanding as of June 30, 2017 and December 31, 2016, respectively	3,001,589	3,003,391
Limited partners' equity	54,170	54,631
Noncontrolling interest - operating partnership
Noncontrolling interest - consolidated joint ventures	4,901	4,901
Total owners' equity	3,060,660	3,062,923
Total liabilities, noncontrolling interest - operating partnership and equity	$ 6,159,635	$ 5,992,813

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parentheticals) - USD ($)	Jun. 30, 2017	Dec. 31, 2016
Deferred financing and leasing costs, accumulated amortization	$ 161,544,000	$ 152,309,000
Limited Partners' common units outstanding	3,528,281	3,530,031
Common shares of beneficial interest, par value per share	$ 0.001	$ 0.001
Common shares of beneficial interest, shares authorized	283,987,000	283,987,000
Common shares of beneficial interest, shares issued	147,304,661	146,993,018
Common shares of beneficial interest, shares outstanding	147,304,661	146,993,018
Liberty Property Limited Partnership [Member]
Deferred financing and leasing costs, accumulated amortization	$ 161,544,000	$ 152,309,000
Limited Partners' common units outstanding	3,528,281	3,530,031
Common shares of beneficial interest, shares outstanding	147,304,661	146,993,018
Series I 2 [Member]
Noncontrolling interest - operating partnership, preferred units outstanding	301,483	301,483
Series I 2 [Member] | Liberty Property Limited Partnership [Member]
Noncontrolling interest - operating partnership, preferred units outstanding	301,483	301,483

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
OPERATING REVENUE
Rental	$ 124,969	$ 139,143	$ 248,350	$ 278,198
Operating expense reimbursement	39,902	47,511	80,402	98,597
Development service fee income	18,259	0	29,744	0
Total operating revenue	183,130	186,654	358,496	376,795
OPERATING EXPENSE
Rental property	17,716	24,745	37,600	53,255
Real estate taxes	23,244	25,202	46,525	50,522
General and administrative	15,282	15,629	32,224	36,619
Depreciation and amortization	45,789	53,545	91,249	107,623
Development service fee expense	17,828	0	28,832	0
Total operating expenses	119,859	119,121	236,430	248,019
Operating income	63,271	67,533	122,066	128,776
OTHER INCOME (EXPENSE)
Interest and other income	1,928	4,992	3,804	9,590
Interest expense	(21,942)	(30,131)	(44,285)	(61,543)
Total other income (expense)	(20,014)	(25,139)	(40,481)	(51,953)
Income before gain on property dispositions, income taxes and equity in earnings of unconsolidated joint ventures	43,257	42,394	81,585	76,823
Gain on property dispositions	5,895	3,832	6,702	24,353
Income taxes	(324)	(752)	(946)	(1,553)
Equity in earnings of unconsolidated joint ventures	3,990	5,583	9,721	10,497
Income from continuing operations	52,818	51,057	97,062	110,120
Net income	52,818	51,057	97,062	110,120
Noncontrolling interest – operating partnership	(1,350)	(1,317)	(2,499)	(2,826)
Noncontrolling interest - consolidated joint ventures	(57)	(113)	(120)	(113)
Net income available to common shareholders	51,411	49,627	94,443	107,181
Comprehensive income attributable to common shareholders
Net income	52,818	51,057	97,062	110,120
Other comprehensive income (loss) - foreign currency translation	7,503	(13,509)	10,680	(18,596)
Other comprehensive (loss) income - derivative instruments	(38)	(435)	275	(1,795)
Other comprehensive income (loss)	7,465	(13,944)	10,955	(20,391)
Total comprehensive income	60,283	37,113	108,017	89,729
Less: comprehensive income attributable to noncontrolling interest	(1,582)	(1,101)	(2,875)	(2,458)
Comprehensive income attributable to common shareholders	$ 58,701	$ 36,012	$ 105,142	$ 87,271
Weighted average number of common shares outstanding
Basic	146,688	145,995	146,602	146,002
Diluted	147,508	146,735	147,355	146,622
Amounts attributable to common shareholders
Net income available to common shareholders	$ 51,411	$ 49,627	$ 94,443	$ 107,181
Liberty Property Limited Partnership [Member]
OPERATING REVENUE
Rental	124,969	139,143	248,350	278,198
Operating expense reimbursement	39,902	47,511	80,402	98,597
Development service fee income	18,259	0	29,744	0
Total operating revenue	183,130	186,654	358,496	376,795
OPERATING EXPENSE
Rental property	17,716	24,745	37,600	53,255
Real estate taxes	23,244	25,202	46,525	50,522
General and administrative	15,282	15,629	32,224	36,619
Depreciation and amortization	45,789	53,545	91,249	107,623
Development service fee expense	17,828	0	28,832	0
Total operating expenses	119,859	119,121	236,430	248,019
Operating income	63,271	67,533	122,066	128,776
OTHER INCOME (EXPENSE)
Interest and other income	1,928	4,992	3,804	9,590
Interest expense	(21,942)	(30,131)	(44,285)	(61,543)
Total other income (expense)	(20,014)	(25,139)	(40,481)	(51,953)
Income before gain on property dispositions, income taxes and equity in earnings of unconsolidated joint ventures	43,257	42,394	81,585	76,823
Gain on property dispositions	5,895	3,832	6,702	24,353
Income taxes	(324)	(752)	(946)	(1,553)
Equity in earnings of unconsolidated joint ventures	3,990	5,583	9,721	10,497
Net income	52,818	51,057	97,062	110,120
Noncontrolling interest - consolidated joint ventures	(57)	(113)	(120)	(113)
Preferred unit distributions	(118)	(118)	(236)	(236)
Net income available to common shareholders	52,643	50,826	96,706	109,771
Comprehensive income attributable to common shareholders
Net income	52,818	51,057	97,062	110,120
Other comprehensive income (loss) - foreign currency translation	7,503	(13,509)	10,680	(18,596)
Other comprehensive (loss) income - derivative instruments	(38)	(435)	275	(1,795)
Other comprehensive income (loss)	7,465	(13,944)	10,955	(20,391)
Total comprehensive income	$ 60,283	$ 37,113	$ 108,017	$ 89,729
Weighted average number of common shares outstanding
Basic	150,216	149,534	150,130	149,541
Diluted	151,036	150,274	150,883	150,161
Net income allocated to general partners	$ 51,411	$ 49,627	$ 94,443	$ 107,181
Net income allocated to limited partners	1,350	1,317	2,499	2,826
Amounts attributable to common shareholders
Income from continuing operations	52,761	50,944	96,942	110,007
Net income available to common shareholders	$ 52,643	$ 50,826	$ 96,706	$ 109,771
Common shares [Member]
Basic:
Income per common share - basic	$ 0.35	$ 0.34	$ 0.64	$ 0.73
Diluted:
Income per common share - diluted	0.35	0.34	0.64	0.73
Distributions per common share or unit	0.40	0.475	0.80	0.95
Common Units [Member] | Liberty Property Limited Partnership [Member]
Basic:
Income per common share - basic	0.35	0.34	0.64	0.73
Diluted:
Income per common share - diluted	0.35	0.34	0.64	0.73
Distributions per common share or unit	$ 0.40	$ 0.475	$ 0.80	$ 0.95

Consolidated Statement of Equit

Consolidated Statement of Equity - USD ($)	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	AOCI Attributable to Parent [Member]	Accumulated Distributions in Excess of Net Income [Member]	Parent [Member]	Noncontrolling interest operating partnership Common [Member]	Noncontrolling interest-consolidated joint ventures [Member]	Liberty Property Limited Partnership [Member]	Liberty Property Limited Partnership [Member]General Partner [Member]	Liberty Property Limited Partnership [Member]Limited Partner [Member]	Liberty Property Limited Partnership [Member]Noncontrolling interest-consolidated joint ventures [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive income - foreign currency translation	$ (18,596,000)								$ (18,596,000)
Other comprehensive income - derivative instruments	(1,795,000)								(1,795,000)
Beginning Balance at Dec. 31, 2016	3,062,923,000	$ 147,000	$ 3,655,910,000	$ (56,031,000)	$ (596,635,000)	$ 3,003,391,000	$ 54,631,000	$ 4,901,000	3,062,923,000	$ 3,003,391,000	$ 54,631,000	$ 4,901,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net proceeds from the issuance of common shares	4,223,000	0	4,223,000	0	0	4,223,000	0	0
Net income	96,826,000	0	0	0	94,443,000	94,443,000	2,263,000	120,000	96,826,000	94,443,000	2,263,000	120,000
Contributions from partners									10,766,000	10,766,000
Distributions	(120,810,000)	0	0	0	(117,737,000)	(117,737,000)	(2,953,000)	(120,000)
Distributions to partners									(120,810,000)	(117,737,000)	(2,953,000)	(120,000)
Share-based compensation	6,543,000	0	6,543,000	0	0	6,543,000	0	0
Other comprehensive income - foreign currency translation	10,680,000	0	0	10,430,000	0	10,430,000	250,000	0	10,680,000	10,430,000	250,000
Other comprehensive income - derivative instruments	275,000	0	0	269,000	0	269,000	6,000	0	275,000	269,000	6,000
Redemption of noncontrolling interests - common units	0	0	27,000	0	0	27,000	(27,000)	0	0	27,000	(27,000)
Ending Balance at Jun. 30, 2017	3,060,660,000	$ 147,000	$ 3,666,703,000	$ (45,332,000)	$ (619,929,000)	$ 3,001,589,000	$ 54,170,000	$ 4,901,000	3,060,660,000	$ 3,001,589,000	$ 54,170,000	$ 4,901,000
Noncontrolling Interest - Operating Partnership (Mezzanine) - Beginning Balance at Dec. 31, 2016	7,537,000								7,537,000
Increase (Decrease) in Temporary Equity [Roll Forward]
Net income (Mezzanine)	236,000								236,000
Distributions (Mezzanine)	(236,000)								(236,000)
Noncontrolling Interest - Operating Partnership (Mezzanine) - Ending Balance at Jun. 30, 2017	$ 7,537,000								$ 7,537,000

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
OPERATING ACTIVITIES
Net income	$ 97,062	$ 110,120
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	92,310	109,047
Amortization of deferred financing costs	1,874	2,004
Equity in earnings of unconsolidated joint ventures	(9,721)	(10,497)
Gain on property dispositions	(6,702)	(24,353)
Share-based compensation/Non-cash compensation	10,500	15,663
Other	(1,712)	(4,424)
Changes in operating assets and liabilities:
Restricted cash	(5,102)	3,390
Accounts receivable	630	1,794
Deferred rent receivable	(10,851)	(8,897)
Prepaid expenses and other assets	10,459	312
Accounts payable	(4,154)	3,877
Accrued interest	(160)	342
Other liabilities	3,399	(17,342)
Net cash provided by operating activities	177,832	181,036
INVESTING ACTIVITIES
Investment in properties - acquisitions	(19,838)	(8,000)
Investment in properties - other	(25,562)	(30,338)
Investments in and advances to unconsolidated joint ventures	(25,333)	(31,372)
Distributions from unconsolidated joint ventures	12,178	35,250
Net proceeds from disposition of properties/land	26,220	139,814
Investment in development in progress	(136,030)	(175,744)
Investment in land held for development	(87,255)	(36,855)
Payment of deferred leasing costs	(18,750)	(15,057)
Investing - Other	26,315	7,842
Net cash used in investing activities	(248,055)	(114,460)
FINANCING ACTIVITIES
Net proceeds from issuance of common shares	4,223	4,341
Share repurchase including shares related to tax withholdings	(4,668)	(45,006)
Repayments of mortgage loans	(3,876)	(22,123)
Proceeds from credit facility	284,000	338,300
Repayments on credit facility	(107,000)	(202,300)
Distribution paid on common shares	(128,703)	(139,742)
Distribution paid on units	(3,569)	(3,847)
Net cash provided by (used in) financing activities	40,407	(70,377)
Net decrease in cash and cash equivalents	(29,816)	(3,801)
Increase (decrease) in cash and cash equivalents related to foreign currency translation	922	(2,212)
Cash and cash equivalents at beginning of period	43,642	35,353
Cash and cash equivalents at end of period	14,748	29,340
Liberty Property Limited Partnership [Member]
OPERATING ACTIVITIES
Net income	97,062	110,120
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	92,310	109,047
Amortization of deferred financing costs	1,874	2,004
Equity in earnings of unconsolidated joint ventures	(9,721)	(10,497)
Gain on property dispositions	(6,702)	(24,353)
Share-based compensation/Non-cash compensation	10,500	15,663
Other	(1,712)	(4,424)
Changes in operating assets and liabilities:
Restricted cash	(5,102)	3,390
Accounts receivable	630	1,794
Deferred rent receivable	(10,851)	(8,897)
Prepaid expenses and other assets	10,459	312
Accounts payable	(4,154)	3,877
Accrued interest	(160)	342
Other liabilities	3,399	(17,342)
Net cash provided by operating activities	177,832	181,036
INVESTING ACTIVITIES
Investment in properties - acquisitions	(19,838)	(8,000)
Investment in properties - other	(25,562)	(30,338)
Investments in and advances to unconsolidated joint ventures	(25,333)	(31,372)
Distributions from unconsolidated joint ventures	12,178	35,250
Net proceeds from disposition of properties/land	26,220	139,814
Investment in development in progress	(136,030)	(175,744)
Investment in land held for development	(87,255)	(36,855)
Payment of deferred leasing costs	(18,750)	(15,057)
Investing - Other	26,315	7,842
Net cash used in investing activities	(248,055)	(114,460)
FINANCING ACTIVITIES
Repayments of mortgage loans	(3,876)	(22,123)
Proceeds from credit facility	284,000	338,300
Repayments on credit facility	(107,000)	(202,300)
Capital contributions	4,223	4,341
Distributions to partners/noncontrolling interests	(136,940)	(188,595)
Net cash provided by (used in) financing activities	40,407	(70,377)
Net decrease in cash and cash equivalents	(29,816)	(3,801)
Increase (decrease) in cash and cash equivalents related to foreign currency translation	922	(2,212)
Cash and cash equivalents at beginning of period	43,642	35,353
Cash and cash equivalents at end of period	$ 14,748	$ 29,340

Organization and Basis of Prese

Organization and Basis of Presentation	6 Months Ended
	Jun. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block]	Organization and Basis of Presentation Organization Liberty Property Trust (the “Trust”) is a self-administered and self-managed Maryland real estate investment trust (a “REIT”). Substantially all of the Trust’s assets are owned directly or indirectly, and substantially all of the Trust’s operations are conducted directly or indirectly, by its subsidiary, Liberty Property Limited Partnership, a Pennsylvania limited partnership (the “Operating Partnership” and, together with the Trust and their consolidated subsidiaries, the “Company”). The Trust is the sole general partner and also a limited partner of the Operating Partnership, owning 97.7% of the common equity of the Operating Partnership at June 30, 2017 . The Company owns and operates industrial properties nationally and owns and operates office properties in a focused group of office markets. Additionally, the Company owns certain assets in the United Kingdom. Unless otherwise indicated, the notes to the Consolidated Financial Statements apply to both the Trust and the Operating Partnership. The terms the “Company,” “we,” “our” and “us” mean the Trust and Operating Partnership collectively. The Operating Partnership is a variable interest entity ("VIE") of the Trust as the limited partners do not have substantive kick-out or participating rights. The Trust is the primary beneficiary of the Operating Partnership as it has the power to direct the activities of the Operating Partnership and the rights to absorb 97.7% of the net income of the Operating Partnership. The Trust has no significant assets or liabilities other than its investment in the Operating Partnership. As the Operating Partnership is already consolidated in the balance sheets of the Trust, the identification of this entity as a VIE has no impact on the consolidated financial statements of the Trust. In addition, the Company holds a 20% interest in Liberty/Comcast 1701 JFK Boulevard, LP which was determined to be a VIE. The Company determined that it is not the primary beneficiary as the Company and its third party partner share control of the joint venture. The Company's maximum exposure to loss is equal to its equity investment in the joint venture which was $17.7 million and $18.7 million as of June 30, 2017 and December 31, 2016, respectively. Basis of Presentation The accompanying unaudited consolidated financial statements of the Company have been prepared in accordance with United States generally accepted accounting principles (“US GAAP”) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by US GAAP for complete financial statements and should be read in conjunction with the consolidated financial statements and notes thereto included in the Annual Report on Form 10-K of the Company for the year ended December 31, 2016 . In the opinion of management, all adjustments (consisting solely of normal recurring adjustments) necessary for a fair presentation of the financial statements for these interim periods have been included. The results of interim periods are not necessarily indicative of the results to be obtained for a full fiscal year. In the fourth quarter of 2016, the Company entered into an agreement relating to the development, for a fee, of an office building at its Camden Waterfront project in Camden, NJ. Project revenues and related costs and expenses are presented on a gross basis as "Development service fee income" and "Development service fee expense" in the Consolidated Statements of Comprehensive Income. Additionally, at the same time, the Company began classifying development fees and expenses relating to its development fee arrangements for certain unconsolidated joint venture projects in a manner consistent with the Camden project described above. Previously, development service fee income relating to its unconsolidated joint ventures had been classified as other income and development service fee expense had been classified as general and administrative expense in amounts as follows: Three months ended Six months ended June 30, 2016 June 30, 2016 Other income $ 1,198 $ 2,570 General and administrative $ 1,054 $ 2,152 In the first quarter of 2017, the Company adopted ASU 2016-09, Improvements to Employee Share-Based Payment Accounting (“ASU 2016-09”), which requires the Company to reclassify shares withheld for tax withholding purposes on share-based compensation awards from operating activities to financing activities. As a result of the adoption, a $4.1 million cash outflow has been reclassified in the June 30, 2016 consolidated statement of cash flows from operating activities to financing activities. Recently Issued Accounting Standards In May 2014, the Financial Accounting Standards Board ("FASB") issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606) ("ASU 2014-09"), which supersedes nearly all existing revenue recognition guidance (except revenue in the scope of other accounting standards, including standards related to leasing). Subsequently, the FASB issued the following standards related to ASU 2014-09: ASU 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (“ASU 2016-08”); ASU 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing (“ASU 2016-10”); and ASU 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients (“ASU 2016-12”). The Company must adopt ASU 2016-08, ASU 2016-10 and ASU 2016-12 with ASU 2014-09 (collectively, the “New Revenue Standards”) effective January 1, 2018. The New Revenue Standards clarify the required factors that an entity must consider when recognizing revenue and require additional disclosures concerning contracts with customers, judgments concerning revenue recognition, and assets recognized for the costs to obtain or fulfill a contract. The New Revenue Standards also provide guidance regarding the measurement of gains and losses relative to the sale of certain nonfinancial assets, including real estate. The Company has created an implementation plan and is progressing in its assessment of the impact of the New Revenue Standards on various revenue streams and evaluating the qualitative and quantitative disclosure guidance. The Company does not expect the New Revenue Standards to have a material impact on the measurement and recognition of gains and losses on the sale of properties. The New Revenue Standards may impact revenue recognized under the percentage of completion method. The Company is currently assessing whether there will an impact on the amount and timing of recognizing its development service fee income which is currently accounted for under the percentage of completion method based on applicable costs incurred and estimated to be incurred. The Company expects the adoption of the New Revenue Standards to have an impact on its business processes, financial reporting disclosures, and internal controls over financial reporting (“ICFR”). The Company plans to adopt the New Revenue Standards using the modified retrospective method. Significant assessment and implementation matters to be addressed prior to adopting the New Revenue Standards include completing a review of customer contracts, determining the impact the new accounting standard will have on the Company’s financial statements and related disclosures, and updating, as needed, the Company’s business processes, systems, and controls required to comply with the New Revenue Standards. Upon completion of the Company’s implementation plan and evaluation of the remaining revenue contracts, the Company will adopt additional controls around ICFR and its business processes for any new and existing revenue arrangements. The Company is on target to complete its assessment of the new revenue standards and the impact on the Company’s financial statements and related disclosures as of January 1, 2018. In February 2016, the FASB issued ASU 2016-02, Leases ("ASU 2016-02"). ASU 2016-02 amends the existing accounting standards for lease accounting, including requiring lessees to recognize most leases on their balance sheets and making targeted changes to lessor accounting. ASU 2016-02 is effective for the Company beginning January 1, 2019. Early adoption of ASU 2016-02 is permitted. The standard requires a modified retrospective transition approach for all leases existing at, or entered into after, the date of initial application, with an option to use certain transition relief. For leases in which the Company is the lessor, the standard requires that the lease and non-lease components of the lease agreement should be separated. Revenue related to the lease component of the contract will be recognized on a straight-line basis, while revenue related to the non-lease component will be recognized under the provisions of ASU 2014-09 (see above). For lease agreements longer than one year in which the Company is the lessee, the Company will measure the present value of the future lease payments and recognize a right-of-use asset and corresponding lease liability on its balance sheet. In addition, the new standard states that only direct leasing costs may be capitalized. The Company is evaluating the impact ASU 2016-02 will have on its financial position and results of operations. In August 2016, the FASB issued ASU 2016-15, Classification of Certain Cash Receipts and Cash Payments (“ASU 2016-15”). ASU 2016-15 is designed to clarify how entities should classify cash receipts and cash payments in the statement of cash flows. ASU 2016-15 is effective for the Company beginning January 1, 2018. Early adoption of ASU 2016-15 is permitted. The standard requires retrospective application unless it is impracticable to do so. The Company is evaluating the impact ASU 2016-15 will have on its statement of cash flows. In February 2017, the FASB issued ASU 2017-05, Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Nonfinancial Assets ("ASU 2017-05"). ASU 2017-05 is designed to provide guidance on how to recognize gain and losses on sales, including partial sale, of nonfinancial assets to noncustomers. ASU 2017-05 is effective for the Company beginning January 1, 2018. Early adoption is permitted but the standard is required to be adopted concurrently with ASU 2014-09. The Company is evaluating the impact ASU 2017-05 will have on the Company's financial position and results of operations. In May 2017, the FASB issued ASU 2017-09, Scope of Modification Accounting ("ASU 2017-09"). ASU 2017-09 clarifies when changes to the terms or conditions of a share-based payment award must be accounted for as modifications. ASU 2017-09 is effective for the Company beginning January 1, 2018. Early adoption is permitted. The new guidance will be applied prospectively to awards modified on or after the adoption date. The Company is evaluating the impact ASU 2017-09 will have on the Company's financial position and results of operations.

Income per Common Share of the

Income per Common Share of the Trust	6 Months Ended
	Jun. 30, 2017
Earnings Per Share [Abstract]
Earnings Per Share [Text Block]	Income per Common Share of the Trust The following table sets forth the computation of basic and diluted income per common share of the Trust (in thousands except per share amounts): For the Three Months Ended For the Three Months Ended June 30, 2017 June 30, 2016 Income (Numerator) Weighted Average Shares (Denominator) Per Share Income (Numerator) Weighted Average Shares (Denominator) Per Share Net income available to common shareholders - basic $ 51,411 146,688 $ 0.35 $ 49,627 145,995 $ 0.34 Dilutive shares for long-term compensation plans — 820 — 740 Net income available to common shareholders - diluted $ 51,411 147,508 $ 0.35 $ 49,627 146,735 $ 0.34 For the Six Months Ended For the Six Months Ended June 30, 2017 June 30, 2016 Income (Numerator) Weighted Average Shares (Denominator) Per Share Income (Numerator) Weighted Average Shares (Denominator) Per Share Net income available to common shareholders - basic $ 94,443 146,602 $ 0.64 $ 107,181 146,002 $ 0.73 Dilutive shares for long-term compensation plans — 753 — 620 Net income available to common shareholders - diluted $ 94,443 147,355 $ 0.64 $ 107,181 146,622 $ 0.73 Dilutive shares for long-term compensation plans represent the unvested common shares outstanding during the periods as well as the dilutive effect of outstanding options. There were no anti-dilutive options excluded from the computation of diluted income per common share for the three and six months ended June 30, 2017 as compared to 885,000 and 1,668,000 , respectively, for the same periods in 2016 . During the three and six months ended June 30, 2017 , 77,000 and 88,000 common shares, respectively, were issued upon the exercise of options. During the year ended December 31, 2016 , 369,000 common shares were issued upon the exercise of options. Share Repurchase In August 2015, the Company’s Board of Trustees authorized a share repurchase plan under which the Company may purchase up to $250 million of the Company’s outstanding common shares through August 7, 2017. Purchases made pursuant to the program may be made in either the open market or in privately negotiated transactions from time to time as permitted by securities laws and other legal requirements. There were no purchases under the plan during the three or six months ended June 30, 2017 .

Income per Common Unit of the O

Income per Common Unit of the Operating Partnership	6 Months Ended
	Jun. 30, 2017
Earnings Per Unit, Basic and Diluted [Line Items]
Earnings Per Share [Text Block]	Income per Common Share of the Trust The following table sets forth the computation of basic and diluted income per common share of the Trust (in thousands except per share amounts): For the Three Months Ended For the Three Months Ended June 30, 2017 June 30, 2016 Income (Numerator) Weighted Average Shares (Denominator) Per Share Income (Numerator) Weighted Average Shares (Denominator) Per Share Net income available to common shareholders - basic $ 51,411 146,688 $ 0.35 $ 49,627 145,995 $ 0.34 Dilutive shares for long-term compensation plans — 820 — 740 Net income available to common shareholders - diluted $ 51,411 147,508 $ 0.35 $ 49,627 146,735 $ 0.34 For the Six Months Ended For the Six Months Ended June 30, 2017 June 30, 2016 Income (Numerator) Weighted Average Shares (Denominator) Per Share Income (Numerator) Weighted Average Shares (Denominator) Per Share Net income available to common shareholders - basic $ 94,443 146,602 $ 0.64 $ 107,181 146,002 $ 0.73 Dilutive shares for long-term compensation plans — 753 — 620 Net income available to common shareholders - diluted $ 94,443 147,355 $ 0.64 $ 107,181 146,622 $ 0.73 Dilutive shares for long-term compensation plans represent the unvested common shares outstanding during the periods as well as the dilutive effect of outstanding options. There were no anti-dilutive options excluded from the computation of diluted income per common share for the three and six months ended June 30, 2017 as compared to 885,000 and 1,668,000 , respectively, for the same periods in 2016 . During the three and six months ended June 30, 2017 , 77,000 and 88,000 common shares, respectively, were issued upon the exercise of options. During the year ended December 31, 2016 , 369,000 common shares were issued upon the exercise of options. Share Repurchase In August 2015, the Company’s Board of Trustees authorized a share repurchase plan under which the Company may purchase up to $250 million of the Company’s outstanding common shares through August 7, 2017. Purchases made pursuant to the program may be made in either the open market or in privately negotiated transactions from time to time as permitted by securities laws and other legal requirements. There were no purchases under the plan during the three or six months ended June 30, 2017 .
Liberty Property Limited Partnership [Member]
Earnings Per Unit, Basic and Diluted [Line Items]
Earnings Per Share [Text Block]	Income per Common Unit of the Operating Partnership The following table sets forth the computation of basic and diluted income per common unit of the Operating Partnership (in thousands, except per unit amounts): For the Three Months Ended For the Three Months Ended June 30, 2017 June 30, 2016 Income (Numerator) Weighted Average Units (Denominator) Per Unit Income (Numerator) Weighted Average Units (Denominator) Per Unit Net income - net of noncontrolling interest - consolidated joint ventures $ 52,761 $ 50,944 Less: Preferred unit distributions (118 ) (118 ) Net income available to common unitholders - basic $ 52,643 150,216 $ 0.35 $ 50,826 149,534 $ 0.34 Dilutive units for long-term compensation plans — 820 — 740 Net income available to common unitholders - diluted $ 52,643 151,036 $ 0.35 $ 50,826 150,274 $ 0.34 For the Six Months Ended For the Six Months Ended June 30, 2017 June 30, 2016 Income (Numerator) Weighted Average Units (Denominator) Per Unit Income (Numerator) Weighted Average Units (Denominator) Per Unit Net income - net of noncontrolling interest - consolidated joint ventures $ 96,942 $ 110,007 Less: Preferred unit distributions (236 ) (236 ) Net income available to common unitholders - basic 96,706 150,130 $ 0.64 109,771 149,541 $ 0.73 Dilutive units for long-term compensation plans — 753 — 620 Net income available to common unitholders - diluted $ 96,706 150,883 $ 0.64 $ 109,771 150,161 $ 0.73 Dilutive units for long-term compensation plans represent the unvested common units outstanding during the periods as well as the dilutive effect of outstanding options. There were no anti-dilutive options excluded from the computation of diluted income per common unit for the three and six months ended June 30, 2017 as compared to 885,000 and 1,668,000 , respectively, for the same periods in 2016 . During the three and six months ended June 30, 2017 , 77,000 and 88,000 common units, respectively, were issued upon exercise of options. During the year ended December 31, 2016 , 369,000 common units were issued upon the exercise of options. Share Repurchase In August 2015, the Company’s Board of Trustees authorized a share repurchase plan under which the Company may purchase up to $250 million of the Company’s outstanding common units through August 7, 2017. Purchases made pursuant to the program may be made in either the open market or in privately negotiated transactions from time to time as permitted by securities laws and other legal requirements. There were no purchases under the plan during the three or six months ended June 30, 2017 .

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income	6 Months Ended
	Jun. 30, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss) Note [Text Block]	Accumulated Other Comprehensive Loss The following table sets forth the components of Accumulated Other Comprehensive Loss (in thousands): As of and for the six months ended June 30, 2017 2016 Foreign Currency Translation: Beginning balance $ (56,767 ) $ (22,023 ) Translation adjustment 10,680 (18,596 ) Ending balance (46,087 ) (40,619 ) Derivative Instruments: Beginning balance (455 ) (865 ) Unrealized loss (41 ) (2,354 ) Reclassification adjustment (1) 316 559 Ending balance (180 ) (2,660 ) Total accumulated other comprehensive loss (46,267 ) (43,279 ) Less: portion included in noncontrolling interest – operating partnership 935 863 Total accumulated other comprehensive loss included in shareholders' equity/owners' equity $ (45,332 ) $ (42,416 ) (1) Amounts reclassified out of Accumulated Other Comprehensive Loss/General & Limited Partner's Equity into contractual interest expense.

Real Estate

Real Estate	6 Months Ended
	Jun. 30, 2017
Property, Plant and Equipment [Abstract]
Disposal Groups, Including Discontinued Operations, Disclosure [Text Block]	Real Estate During the three and six months ended June 30, 2017, the Company acquired one property for a purchase price of $19.1 million . This property was under development when acquired and contains 101,000 square feet of leaseable space. The property is located in the Company's Southern California reportable segment. Information on the operating properties and land parcels the Company sold during the three and six months ended June 30, 2017 is as follows: Three Months Ended June 30, 2017 Six Months Ended June 30, 2017 Number of Buildings Acres of Developable Land Leaseable Square Feet Gross Proceeds (in thousands) Number of Buildings Acres of Developable Land Leaseable Square Feet Gross Proceeds (in thousands) Chicago/Minneapolis 1 — 31,116 $ 3,100 1 — 31,116 $ 3,100 Florida — 11 — 2,636 — 11 — 2,636 Houston — 7 — 1,995 — 7 — 1,995 Philadelphia — 2 — 6,904 — 2 — 6,904 Southeastern PA 1 3 62,386 6,975 2 3 95,413 9,050 Other — 6 — 3,739 — 6 — 3,739 2 29 93,502 $ 25,349 3 29 126,529 $ 27,424 As of June 30, 2017, the Company classified 4.9 acres of land held for development with a total carrying value of $2.7 million as assets held for sale. This land is located in the Company's Florida reportable segment. The land was sold subsequent to June 30, 2017.

Segment Information

Segment Information	6 Months Ended
	Jun. 30, 2017
Segment Reporting [Abstract]
Segment Information	Segment Information The Company owns and operates industrial properties nationally and owns and operates office properties in a focused group of office markets. Additionally, the Company owns certain assets in the United Kingdom. During the six months ended June 30, 2017, the Company realigned its reportable segments as follows: • Carolinas/Richmond; • Chicago/Minneapolis; • Florida; • Houston; • Lehigh/Central PA; • Philadelphia; • Southeastern PA; and • United Kingdom. Certain other segments are aggregated into an "Other" category which includes the reportable segments: Arizona; Atlanta; Cincinnati/Columbus/Indianapolis; Dallas; DC Metro; New Jersey; and Southern California. Comparative prior periods have been restated to reflect current segment disclosures. The Company evaluates the performance of its reportable segments based on segment net operating income (“SNOI”). SNOI is defined as net operating income (rental revenue and operating expense reimbursements less property and real estate tax expenses) less amortization of lease transaction costs and other operating expenses which relate directly to the management and operation of the assets within each reportable segment. The Company's accounting policies for the segments are the same as those used in the Company's consolidated financial statements. There are no material inter-segment transactions. The operating information by reportable segment is as follows (in thousands): Three Months Six Months Ended June 30, Ended June 30, 2017 2016 2017 2016 Operating revenue Carolinas/Richmond $ 18,225 $ 16,174 $ 36,282 $ 31,934 Chicago/Minneapolis 15,767 21,891 31,642 43,430 Florida 14,482 27,798 28,730 57,115 Houston 14,779 14,204 29,553 28,971 Lehigh/Central PA 39,815 33,782 81,350 68,025 Philadelphia 10,928 10,386 22,363 20,741 Southeastern PA 15,127 24,343 29,742 50,226 United Kingdom 3,262 3,525 6,431 7,077 Other 32,166 34,444 62,538 69,441 Segment-level operating revenue 164,551 186,547 328,631 376,960 Reconciliation to total operating revenues Development service fee income 18,259 — 29,744 — Other 320 107 121 (165 ) Total operating revenue $ 183,130 $ 186,654 $ 358,496 $ 376,795 SNOI Carolinas/Richmond $ 13,094 $ 11,219 $ 26,077 $ 22,059 Chicago/Minneapolis 10,011 11,872 19,360 23,243 Florida 10,003 16,741 19,510 34,788 Houston 7,761 8,036 14,562 16,869 Lehigh/Central PA 29,083 24,755 58,661 48,957 Philadelphia 8,475 7,981 17,234 15,339 Southeastern PA 8,507 14,549 16,619 28,300 United Kingdom 1,649 2,438 3,506 4,842 Other 21,935 22,953 42,191 45,779 SNOI 110,518 120,544 217,720 240,176 Reconciliation to net income Interest expense (21,942 ) (30,131 ) (44,285 ) (61,543 ) Depreciation/amortization expense (1) (33,115 ) (39,161 ) (66,308 ) (78,959 ) Gain on property dispositions 5,895 3,832 6,702 24,353 Equity in earnings of unconsolidated joint ventures 3,990 5,583 9,721 10,497 General and administrative expense (1) (11,047 ) (10,135 ) (23,301 ) (24,927 ) Income taxes (1) 104 (653 ) (176 ) (1,222 ) Other (1,585 ) 1,178 (3,011 ) 1,745 Net income $ 52,818 $ 51,057 $ 97,062 $ 110,120 (1) Excludes costs which are included in determining SNOI. The Company's total assets by reportable segment as of June 30, 2017 and December 31, 2016 is as follows (in thousands): June 30, 2017 December 31, 2016 Carolinas/Richmond $ 512,329 $ 503,920 Chicago/Minnesota 609,962 616,298 Florida 507,873 514,431 Houston 529,946 530,438 Lehigh/Central PA 1,350,454 1,311,815 Philadelphia 610,025 557,510 Southeastern PA 271,035 262,155 United Kingdom 227,793 189,766 Other 1,487,741 1,403,431 Segment-level total assets 6,107,158 5,889,764 Corporate Other 52,477 103,049 Total assets $ 6,159,635 $ 5,992,813

Accounting for the Impairment o

Accounting for the Impairment of Long-Lived Assets and Fee Development Contracts	6 Months Ended
	Jun. 30, 2017
Property, Plant and Equipment [Abstract]
Asset Impairment Charges [Text Block]	Accounting for the Impairment of Long-Lived Assets and Fee Development Contracts Asset Impairment The Company disposes of and anticipates the potential disposition of certain properties prior to the end of their remaining useful lives. There were no impairments recognized during the three or six months ended June 30, 2017 or 2016. The Company has applied reasonable estimates and judgments in evaluating each of its properties and land held for development and has determined that there were no valuation adjustments necessary at June 30, 2017 . Should external or internal circumstances change requiring the need to shorten the holding periods or adjust the estimated future cash flows of the Company’s assets, the Company could be required to record impairment charges in the future. Fee Development Contracts From time to time, the Company enters into contracts to develop properties on a fee basis for joint ventures in which the Company holds an interest or for unrelated third parties. In these cases the Company typically agrees to be responsible for all aspects of the development of the project (and, in certain instances, related infrastructure) and to guarantee the timely lien-free completion of construction of the project and the payment, subject to certain exceptions, of cost overruns incurred in the development of the project. If the Company encounters construction delays or unexpected costs in the development of these projects or is otherwise unable to recover the costs it incurs, the resulting unrecovered costs and potential payments to customers could generate losses that would adversely affect the Company's cash flow and net income. On a quarterly basis, the Company applies reasonable estimates and judgments to assess whether or not it is necessary to accrue any estimated future losses with respect to such contracts. There were no such losses recognized during the three or six months ended June 30, 2017 or 2016. Should external or internal circumstances change requiring the Company to adjust the estimated future cash flows from these development contracts or that suggest that such development contracts may result in a loss, the Company could be required to record losses in the future.

Noncontrolling Interests of the

Noncontrolling Interests of the Trust	6 Months Ended
	Jun. 30, 2017
Stockholders' Equity Attributable to Noncontrolling Interest [Abstract]
Noncontrolling Interests	Noncontrolling Interests of the Trust Noncontrolling interests in the accompanying financial statements represent the interests of the common and preferred units in the Operating Partnership not held by the Trust. In addition, noncontrolling interests include third-party ownership interests in consolidated joint venture investments. Common units The common units of the Operating Partnership not held by the Trust outstanding as of June 30, 2017 have the same economic characteristics as common shares of the Trust. The 3.5 million outstanding common units of the Operating Partnership not held by the Trust share proportionately in the net income or loss and in any distributions of the Operating Partnership. The common units of the Operating Partnership not held by the Trust are redeemable at any time at the option of the holder. The Trust, as the sole general partner of the Operating Partnership, may at its option elect to settle the redemption in cash or through the exchange on a one-for-one basis with unregistered common shares of the Trust. The market value of the 3.5 million outstanding common units based on the closing price of the common shares of the Trust at June 30, 2017 was $ 143.6 million .

Limited Partners' Equity of the

Limited Partners' Equity of the Operating Partnership	6 Months Ended
	Jun. 30, 2017
Preferred Units [Line Items]
Noncontrolling Interest Disclosure [Text Block]	Noncontrolling Interests of the Trust Noncontrolling interests in the accompanying financial statements represent the interests of the common and preferred units in the Operating Partnership not held by the Trust. In addition, noncontrolling interests include third-party ownership interests in consolidated joint venture investments. Common units The common units of the Operating Partnership not held by the Trust outstanding as of June 30, 2017 have the same economic characteristics as common shares of the Trust. The 3.5 million outstanding common units of the Operating Partnership not held by the Trust share proportionately in the net income or loss and in any distributions of the Operating Partnership. The common units of the Operating Partnership not held by the Trust are redeemable at any time at the option of the holder. The Trust, as the sole general partner of the Operating Partnership, may at its option elect to settle the redemption in cash or through the exchange on a one-for-one basis with unregistered common shares of the Trust. The market value of the 3.5 million outstanding common units based on the closing price of the common shares of the Trust at June 30, 2017 was $ 143.6 million .
Liberty Property Limited Partnership [Member]
Preferred Units [Line Items]
Noncontrolling Interest Disclosure [Text Block]	Limited Partners' Equity and Noncontrolling Interest of the Operating Partnership Limited partners' equity in the accompanying financial statements represents the interests of the common and preferred units in the Operating Partnership not held by the Trust. The Operating Partnership's noncontrolling interest includes third-party ownership interests in consolidated joint venture investments. Common units The common units outstanding have the same economic characteristics as common shares of the Trust. The 3.5 million outstanding common units as of June 30, 2017 not held by the Trust are the limited partners' equity - common units held by persons and entities other than the Trust. The common units of the Operating Partnership not held by the Trust are redeemable at any time at the option of the holder. The Trust, as the sole general partner of the Operating Partnership, may at its option elect to settle the redemption in cash or through the exchange on a one-for-one basis with unregistered common shares of the Trust. The market value of the 3.5 million outstanding common units at June 30, 2017 based on the closing price of the common shares of the Trust at June 30, 2017 was $ 143.6 million .

Noncontrolling Interest - Opera

Noncontrolling Interest - Operating Partnership/Limited Partners' Equity - Preferred Units	6 Months Ended
	Jun. 30, 2017
Temporary Equity [Line Items]
Stockholders' Equity Note Disclosure [Text Block]	Noncontrolling Interest - Operating Partnership/Limited Partners' Equity - Preferred Units As of June 30, 2017 , the Company had outstanding the following cumulative preferred units of the Operating Partnership: ISSUE AMOUNT UNITS LIQUIDATION PREFERENCE DIVIDEND RATE (in 000’s) Series I-2 $ 7,537 301 $25 6.25 % The preferred units are putable at the holder's option at any time and are callable at the Operating Partnership's option after a stated period of time for cash.

Disclosure of Fair Value of Fin

Disclosure of Fair Value of Financial Instruments	6 Months Ended
	Jun. 30, 2017
Debt Instrument, Fair Value Disclosure [Abstract]
Disclosure of Fair Value of Financial Instruments	Fair Value of Financial Instruments ASC 820, Fair Value Measurements and Disclosures, gives guidance on the fair value measurement of a financial asset or liability. Inputs used to develop fair value are classified in one of three categories: Level 1 inputs (quoted prices (unadjusted) in active markets for identical assets or liabilities), Level 2 inputs (inputs other than quoted prices that are observable for the asset or liability, either directly or indirectly) and Level 3 inputs (unobservable inputs for the asset or liability). The following disclosure of estimated fair value was determined by management using available market information and appropriate valuation methodologies. However, considerable judgment is necessary to interpret market data and develop estimated fair value. Accordingly, the following estimates are not necessarily indicative of the amounts the Company could have realized on disposition of the financial instruments at June 30, 2017 and December 31, 2016 . The use of different market assumptions and/or estimation methodologies may have a material effect on the estimated fair value amounts. The carrying value of cash and cash equivalents, restricted cash, accounts receivable, accounts payable, accrued interest, dividend and distributions payable and other liabilities are reasonable estimates of fair value because of the short-term nature of these instruments. The carrying value of the outstanding amounts under the Company's credit facility is a reasonable estimate of fair value because interest rates float at a rate based on LIBOR. The Company determines the fair value of its interest rate swaps by using the standard methodology of netting discounted future fixed cash payments with the discounted expected variable cash receipts. These variable cash receipts of interest rate swaps are based on expectations of future LIBOR interest rates (forward curves) estimated by observing market LIBOR interest rate curves. This is a Level 2 fair value calculation. Also, credit valuation adjustments are factored into the fair value calculations to account for potential nonperformance risk. These credit valuation adjustments were concluded to be not significant inputs for the fair value calculations for the periods presented. See Note 13 - Derivative Instruments. The Company used a discounted cash flow model to determine the estimated fair value of its debt as of June 30, 2017 and December 31, 2016 . This is a Level 3 fair value calculation. The inputs used in preparing the discounted cash flow model include actual maturity dates and scheduled cash flows as well as estimates for market value discount rates. The Company updates the discounted cash flow model on a quarterly basis to reflect any changes in the Company's debt holdings and changes to discount rate assumptions. The following summarizes the fair value of the Company's mortgage loans and unsecured notes as of December 31, 2016 and June 30, 2017 (in thousands): Mortgage Loans Unsecured Notes Carrying Value Fair Value Carrying Value Fair Value As of December 31, 2016 $ 276,650 $ 286,684 $ 2,280,286 $ 2,340,762 As of June 30, 2017 $ 271,851 $ 283,911 $ 2,281,650 $ 2,364,004

Unconsolidated Joint Ventures

Unconsolidated Joint Ventures	6 Months Ended
	Jun. 30, 2017
Equity Method Investments and Joint Ventures [Abstract]
Equity Method Investments and Joint Ventures Disclosure [Text Block]	Unconsolidated Joint Ventures Cambridge Medipark Ltd During the three and six months ended June 30, 2017 and 2016, Cambridge Medipark, Ltd (a joint venture in which the Company holds a 50% interest) recognized gains on the sale of land leasehold interests. The Company's share of these gains was $1.5 million and $4.5 million , respectively, for the three and six months ended June 30, 2017 compared to $312,000 and $206,000 , respectively, for the same periods in 2016.

Derivative Instruments

Derivative Instruments	6 Months Ended
	Jun. 30, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Interest rate swaps [Text Block]	Derivative Instruments The Company borrows funds at a combination of fixed and variable rates. Borrowings under the Company's revolving credit facility and certain bank mortgage loans bear interest at variable rates. Our long-term debt typically bears interest at fixed rates. The Company's interest rate risk management objectives are to limit generally the impact of interest rate changes on earnings and cash flows and to lower the Company's overall borrowing costs. To achieve these objectives, from time to time, the Company enters into interest rate hedge contracts such as collars, swaps, caps and treasury lock agreements in order to mitigate our interest rate risk with respect to various debt instruments. The Company generally does not hold or issue these derivative contracts for trading or speculative purposes. The interest rate on all of the Company's variable rate debt is generally adjusted at one or three month intervals, subject to settlements under interest rate hedge contracts. Interest rate swaps involve the receipt of variable-rate amounts from a counterparty in exchange for making fixed-rate payments over the life of the agreements without exchange of the underlying notional amount. The effective portion of changes in the fair value of derivatives designated and that qualify as cash flow hedges is recorded in accumulated other comprehensive loss (for the Trust) and general partner's equity and limited partners ’ equity - common units (for the Operating Partnership) and is subsequently reclassified into interest expense in the period that the hedged forecasted transaction affects earnings. The Company determines the fair value of its interest rate swaps by using the standard methodology of netting discounted future fixed cash payments with the discounted expected variable cash receipts. These variable cash receipts of interest rate swaps are based on expectations of future LIBOR interest rates (forward curves) estimated by observing market LIBOR interest rate curves. This is a Level 2 fair value calculation. Also, credit valuation adjustments are factored into the fair value calculations to account for potential nonperformance risk. These credit valuation adjustments were concluded to be not significant inputs for the fair value calculations for the periods presented. The Company holds an interest in three interest rate swap contracts (“Swaps”) that eliminate the impact of changes in interest rates on the payments required under variable rate mortgages. The Swaps had aggregate notional amounts of $97.6 million and $98.9 million at June 30, 2017 and December 31, 2016 , respectively, and expire at various dates between 2018 and 2020 . The Company accounts for the effective portion of changes in the fair value of a derivative in accumulated other comprehensive loss and subsequently reclassifies the effective portion to earnings over the term that the hedged transaction affects earnings. The Company accounts for the ineffective portion of changes in the fair value of a derivative directly in earnings. The following table presents the location in the financial statements of the gains or losses recognized related to the Company’s cash flow hedges for the three months ended June 30, 2017 and 2016 (in thousands): Three Months Ended Six Months Ended June 30, 2017 June 30, 2016 June 30, 2017 June 30, 2016 Amount of loss related to the effective portion recognized in other comprehensive loss $ (163 ) $ (700 ) $ (25 ) $ (2,343 ) Amount of loss related to the effective portion subsequently reclassified to interest expense $ (129 ) $ (276 ) $ (316 ) $ (559 ) Amount of (loss) gain related to the ineffective portion recognized in interest expense $ (9 ) $ (22 ) $ 14 $ (78 ) The fair value of the Swaps in the amounts of $3.7 million and $4.9 million as of June 30, 2017 and December 31, 2016 , respectively, is included in other liabilities in the accompanying consolidated balance sheets. The Company estimates that $0.2 million will be reclassified from accumulated other comprehensive loss as an increase to interest expense over the next 12 months. The Company has agreements with its derivative counterparties that contain a provision whereby if the Company defaults on any of its indebtedness, including defaults where repayment of the indebtedness has not been accelerated by the lender, then the Company could also be declared in default on its derivative obligations. If the Company were to breach any of the contractual provisions of the derivative contracts, it would be required to settle its obligations under the agreements at their termination value including accrued interest, which totaled approximately $3.7 million as of June 30, 2017 .

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Environmental Matters Substantially all of the Company's properties and land were subject to Phase I Environmental Assessments and when appropriate Phase II Environmental Assessments (collectively, the “Environmental Assessments”) obtained in contemplation of their acquisition by the Company or obtained by predecessor owners prior to the sale of the property or land to the Company. The Environmental Assessments did not reveal, nor is the Company aware of, any non-compliance with environmental laws, environmental liability or other environmental claim that the Company believes would likely have a material adverse effect on the Company. Operating Ground Lease Agreements Future minimum rental payments under the terms of all non-cancelable operating ground leases under which the Company is the lessee, as of June 30, 2017 , were as follows (in thousands): Year Amount 2017 (remaining) $ 825 2018 1,754 2019 1,754 2020 1,754 2021 1,754 2022 and thereafter 34,872 Total $ 42,713 Operating ground lease expense for the three and six months ended June 30, 2017 was $311,000 and $623,000 , respectively, as compared to $237,000 and $493,000 , respectively, for the same periods in 2016 . Legal Matters From time to time, the Company is a party to a variety of legal proceedings, claims and assessments arising in the normal course of business. As of June 30, 2017 there were no legal proceedings, claims or assessments that the Company expects to have a material adverse effect on the Company’s business or financial statements. Other As of June 30, 2017 , the Company had letter of credit obligations of $7.7 million . As of June 30, 2017 , the Company had 27 buildings under development. These buildings are expected to contain, when completed, a total of 6.6 million square feet of leasable space and represent an anticipated aggregate investment of $634.0 million . At June 30, 2017 , development in progress totaled $410.0 million . In addition, as of June 30, 2017 , the Company had invested $15.4 million in deferred leasing costs related to these development buildings. Also, as of June 30, 2017, the Company had a signed commitment for $11.8 million for a build-to-suit development not yet commenced. As of June 30, 2017 , the Company was committed to $18.6 million in improvements on certain buildings and land parcels. As of June 30, 2017 , the Company was committed to $19.4 million in future land acquisitions. The Company expects to complete these purchases during the year ended December 31, 2017. As of June 30, 2017 , the Company was obligated to pay for tenant improvements not yet completed for a maximum of $21.1 million . Unconsolidated joint ventures in which the Company holds an interest, and in another case an unrelated third party, have engaged the Company as the developer of certain development properties pursuant to development agreements. The Company agrees, in consideration for a development fee, to be responsible for all aspects of the development of the properties (and, in certain instances, related infrastructure) and to guarantee the timely lien-free completion of construction of the properties and the payment, subject to certain exceptions, of any cost overruns incurred in the development of the properties. The Company is currently developing three buildings for its unconsolidated joint ventures which represent an anticipated aggregate investment by the joint ventures of $966.7 million . As of June 30, 2017, the Company was also committed to approximately $170.1 million in costs related to its agreement to develop, on a fee basis, an office building and infrastructure improvements for American Water Works in Camden, New Jersey. As of June 30, 2017, $46.7 million of these costs had been incurred. The Company maintains cash and cash equivalents at financial institutions. The combined account balances at each institution typically exceed FDIC insurance coverage and, as a result, there is a concentration of credit risk related to amounts on deposit in excess of FDIC insurance coverage. The Company believes the risk is not significant.

Supplemental Disclosure to Stat

Supplemental Disclosure to Statements of Cash Flows	6 Months Ended
	Jun. 30, 2017
Supplemental Cash Flow Information [Abstract]
Supplemental Disclosure to Statements of Cash Flows	Supplemental Disclosure to Consolidated Statements of Cash Flows The following are supplemental disclosures to the consolidated statements of cash flows for the six months ended June 30, 2017 and 2016 (amounts in thousands): 2017 2016 Write-off of fully depreciated/amortized property and deferred costs $ 19,833 $ 19,002 Write-off of depreciated/amortized property and deferred costs due to sale $ 8,989 $ 33,857 Redemption of noncontrolling interests - common units $ 27 $ — Unrealized gain (loss) on cash flow hedge $ 275 $ (1,795 ) Changes in accrued development capital expenditures $ 13,124 $ 2,383 Capitalized equity-based compensation $ 739 $ 808 Amounts paid in cash for deferred leasing costs incurred in connection with signed leases with tenants are paid in conjunction with improving (acquiring) property, plant and equipment. Such costs are not contained within net real estate. However, they are integral to the completion of a tenant lease and ultimately are related to the improvement and thus the value of the Company’s property, plant and equipment. They are therefore included in investing activities in the Company’s consolidated statements of cash flows.

Subsequent Events (Notes)

Subsequent Events (Notes)	6 Months Ended
	Jun. 30, 2017
Subsequent Event [Line Items]
Subsequent Events [Text Block]	Subsequent Events As of June 30, 2017, the Company had a deferred gain related to a 2015 portfolio sale in the amount of $14.3 million which is recorded in other liabilities in the accompanying balance sheets. Subsequent to June 30, 2017, the contingency related to the sale was settled and the Company recognized the deferred gain in net income. Pursuant to a purchase option contained in its lease agreement, on July 27, 2017, a tenant exercised its option to purchase two properties approximating 1.7 million square feet and 44 acres of land for $249.0 million . The properties and land are in the Lehigh/Central PA segment. The sale is currently anticipated to close in 2017, subject to the satisfaction of certain closing conditions contained in the lease. Upon the closing of the sale, the Company expects to recognize a gain on the sale in the range of $65 million to $70 million .

Organization and Basis of Pre23

Organization and Basis of Presentation (Policy)	6 Months Ended
	Jun. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
New Accounting Pronouncements, Policy [Policy Text Block]	Recently Issued Accounting Standards In May 2014, the Financial Accounting Standards Board ("FASB") issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606) ("ASU 2014-09"), which supersedes nearly all existing revenue recognition guidance (except revenue in the scope of other accounting standards, including standards related to leasing). Subsequently, the FASB issued the following standards related to ASU 2014-09: ASU 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (“ASU 2016-08”); ASU 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing (“ASU 2016-10”); and ASU 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients (“ASU 2016-12”). The Company must adopt ASU 2016-08, ASU 2016-10 and ASU 2016-12 with ASU 2014-09 (collectively, the “New Revenue Standards”) effective January 1, 2018. The New Revenue Standards clarify the required factors that an entity must consider when recognizing revenue and require additional disclosures concerning contracts with customers, judgments concerning revenue recognition, and assets recognized for the costs to obtain or fulfill a contract. The New Revenue Standards also provide guidance regarding the measurement of gains and losses relative to the sale of certain nonfinancial assets, including real estate. The Company has created an implementation plan and is progressing in its assessment of the impact of the New Revenue Standards on various revenue streams and evaluating the qualitative and quantitative disclosure guidance. The Company does not expect the New Revenue Standards to have a material impact on the measurement and recognition of gains and losses on the sale of properties. The New Revenue Standards may impact revenue recognized under the percentage of completion method. The Company is currently assessing whether there will an impact on the amount and timing of recognizing its development service fee income which is currently accounted for under the percentage of completion method based on applicable costs incurred and estimated to be incurred. The Company expects the adoption of the New Revenue Standards to have an impact on its business processes, financial reporting disclosures, and internal controls over financial reporting (“ICFR”). The Company plans to adopt the New Revenue Standards using the modified retrospective method. Significant assessment and implementation matters to be addressed prior to adopting the New Revenue Standards include completing a review of customer contracts, determining the impact the new accounting standard will have on the Company’s financial statements and related disclosures, and updating, as needed, the Company’s business processes, systems, and controls required to comply with the New Revenue Standards. Upon completion of the Company’s implementation plan and evaluation of the remaining revenue contracts, the Company will adopt additional controls around ICFR and its business processes for any new and existing revenue arrangements. The Company is on target to complete its assessment of the new revenue standards and the impact on the Company’s financial statements and related disclosures as of January 1, 2018. In February 2016, the FASB issued ASU 2016-02, Leases ("ASU 2016-02"). ASU 2016-02 amends the existing accounting standards for lease accounting, including requiring lessees to recognize most leases on their balance sheets and making targeted changes to lessor accounting. ASU 2016-02 is effective for the Company beginning January 1, 2019. Early adoption of ASU 2016-02 is permitted. The standard requires a modified retrospective transition approach for all leases existing at, or entered into after, the date of initial application, with an option to use certain transition relief. For leases in which the Company is the lessor, the standard requires that the lease and non-lease components of the lease agreement should be separated. Revenue related to the lease component of the contract will be recognized on a straight-line basis, while revenue related to the non-lease component will be recognized under the provisions of ASU 2014-09 (see above). For lease agreements longer than one year in which the Company is the lessee, the Company will measure the present value of the future lease payments and recognize a right-of-use asset and corresponding lease liability on its balance sheet. In addition, the new standard states that only direct leasing costs may be capitalized. The Company is evaluating the impact ASU 2016-02 will have on its financial position and results of operations. In August 2016, the FASB issued ASU 2016-15, Classification of Certain Cash Receipts and Cash Payments (“ASU 2016-15”). ASU 2016-15 is designed to clarify how entities should classify cash receipts and cash payments in the statement of cash flows. ASU 2016-15 is effective for the Company beginning January 1, 2018. Early adoption of ASU 2016-15 is permitted. The standard requires retrospective application unless it is impracticable to do so. The Company is evaluating the impact ASU 2016-15 will have on its statement of cash flows. In February 2017, the FASB issued ASU 2017-05, Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Nonfinancial Assets ("ASU 2017-05"). ASU 2017-05 is designed to provide guidance on how to recognize gain and losses on sales, including partial sale, of nonfinancial assets to noncustomers. ASU 2017-05 is effective for the Company beginning January 1, 2018. Early adoption is permitted but the standard is required to be adopted concurrently with ASU 2014-09. The Company is evaluating the impact ASU 2017-05 will have on the Company's financial position and results of operations. In May 2017, the FASB issued ASU 2017-09, Scope of Modification Accounting ("ASU 2017-09"). ASU 2017-09 clarifies when changes to the terms or conditions of a share-based payment award must be accounted for as modifications. ASU 2017-09 is effective for the Company beginning January 1, 2018. Early adoption is permitted. The new guidance will be applied prospectively to awards modified on or after the adoption date. The Company is evaluating the impact ASU 2017-09 will have on the Company's financial position and results of operations.

Segment Information (Policies)

Segment Information (Policies)	6 Months Ended
	Jun. 30, 2017
Segment Reporting [Abstract]
Segment Reporting, Policy [Policy Text Block]	The Company evaluates the performance of its reportable segments based on segment net operating income (“SNOI”). SNOI is defined as net operating income (rental revenue and operating expense reimbursements less property and real estate tax expenses) less amortization of lease transaction costs and other operating expenses which relate directly to the management and operation of the assets within each reportable segment.

Disclosure of Fair Value of F25

Disclosure of Fair Value of Financial Instruments Fair Value of Financial Instruments (Policies)	6 Months Ended
	Jun. 30, 2017
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments, Policy [Policy Text Block]	ASC 820, Fair Value Measurements and Disclosures, gives guidance on the fair value measurement of a financial asset or liability. Inputs used to develop fair value are classified in one of three categories: Level 1 inputs (quoted prices (unadjusted) in active markets for identical assets or liabilities), Level 2 inputs (inputs other than quoted prices that are observable for the asset or liability, either directly or indirectly) and Level 3 inputs (unobservable inputs for the asset or liability). The following disclosure of estimated fair value was determined by management using available market information and appropriate valuation methodologies. However, considerable judgment is necessary to interpret market data and develop estimated fair value. Accordingly, the following estimates are not necessarily indicative of the amounts the Company could have realized on disposition of the financial instruments at June 30, 2017 and December 31, 2016 . The use of different market assumptions and/or estimation methodologies may have a material effect on the estimated fair value amounts. The carrying value of cash and cash equivalents, restricted cash, accounts receivable, accounts payable, accrued interest, dividend and distributions payable and other liabilities are reasonable estimates of fair value because of the short-term nature of these instruments. The carrying value of the outstanding amounts under the Company's credit facility is a reasonable estimate of fair value because interest rates float at a rate based on LIBOR. The Company determines the fair value of its interest rate swaps by using the standard methodology of netting discounted future fixed cash payments with the discounted expected variable cash receipts. These variable cash receipts of interest rate swaps are based on expectations of future LIBOR interest rates (forward curves) estimated by observing market LIBOR interest rate curves. This is a Level 2 fair value calculation. Also, credit valuation adjustments are factored into the fair value calculations to account for potential nonperformance risk. These credit valuation adjustments were concluded to be not significant inputs for the fair value calculations for the periods presented. See Note 13 - Derivative Instruments. The Company used a discounted cash flow model to determine the estimated fair value of its debt as of June 30, 2017 and December 31, 2016 . This is a Level 3 fair value calculation. The inputs used in preparing the discounted cash flow model include actual maturity dates and scheduled cash flows as well as estimates for market value discount rates. The Company updates the discounted cash flow model on a quarterly basis to reflect any changes in the Company's debt holdings and changes to discount rate assumptions.

Organization and Basis of Pre26

Organization and Basis of Presentation Basis of Presentation (Tables)	6 Months Ended
	Jun. 30, 2017
Basis of Presentation [Abstract]
Schedule of Adjustments to Previously Reported Financial Statements	Previously, development service fee income relating to its unconsolidated joint ventures had been classified as other income and development service fee expense had been classified as general and administrative expense in amounts as follows: Three months ended Six months ended June 30, 2016 June 30, 2016 Other income $ 1,198 $ 2,570 General and administrative $ 1,054 $ 2,152

Income per Common Share of th27

Income per Common Share of the Trust (Tables)	6 Months Ended
	Jun. 30, 2017
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]	The following table sets forth the computation of basic and diluted income per common share of the Trust (in thousands except per share amounts): For the Three Months Ended For the Three Months Ended June 30, 2017 June 30, 2016 Income (Numerator) Weighted Average Shares (Denominator) Per Share Income (Numerator) Weighted Average Shares (Denominator) Per Share Net income available to common shareholders - basic $ 51,411 146,688 $ 0.35 $ 49,627 145,995 $ 0.34 Dilutive shares for long-term compensation plans — 820 — 740 Net income available to common shareholders - diluted $ 51,411 147,508 $ 0.35 $ 49,627 146,735 $ 0.34 For the Six Months Ended For the Six Months Ended June 30, 2017 June 30, 2016 Income (Numerator) Weighted Average Shares (Denominator) Per Share Income (Numerator) Weighted Average Shares (Denominator) Per Share Net income available to common shareholders - basic $ 94,443 146,602 $ 0.64 $ 107,181 146,002 $ 0.73 Dilutive shares for long-term compensation plans — 753 — 620 Net income available to common shareholders - diluted $ 94,443 147,355 $ 0.64 $ 107,181 146,622 $ 0.73

Income per Common Unit of the28

Income per Common Unit of the Operating Partnership (Tables)	6 Months Ended
	Jun. 30, 2017
Earnings Per Unit, Basic and Diluted [Line Items]
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]	The following table sets forth the computation of basic and diluted income per common share of the Trust (in thousands except per share amounts): For the Three Months Ended For the Three Months Ended June 30, 2017 June 30, 2016 Income (Numerator) Weighted Average Shares (Denominator) Per Share Income (Numerator) Weighted Average Shares (Denominator) Per Share Net income available to common shareholders - basic $ 51,411 146,688 $ 0.35 $ 49,627 145,995 $ 0.34 Dilutive shares for long-term compensation plans — 820 — 740 Net income available to common shareholders - diluted $ 51,411 147,508 $ 0.35 $ 49,627 146,735 $ 0.34 For the Six Months Ended For the Six Months Ended June 30, 2017 June 30, 2016 Income (Numerator) Weighted Average Shares (Denominator) Per Share Income (Numerator) Weighted Average Shares (Denominator) Per Share Net income available to common shareholders - basic $ 94,443 146,602 $ 0.64 $ 107,181 146,002 $ 0.73 Dilutive shares for long-term compensation plans — 753 — 620 Net income available to common shareholders - diluted $ 94,443 147,355 $ 0.64 $ 107,181 146,622 $ 0.73
Liberty Property Limited Partnership [Member]
Earnings Per Unit, Basic and Diluted [Line Items]
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]	The following table sets forth the computation of basic and diluted income per common unit of the Operating Partnership (in thousands, except per unit amounts): For the Three Months Ended For the Three Months Ended June 30, 2017 June 30, 2016 Income (Numerator) Weighted Average Units (Denominator) Per Unit Income (Numerator) Weighted Average Units (Denominator) Per Unit Net income - net of noncontrolling interest - consolidated joint ventures $ 52,761 $ 50,944 Less: Preferred unit distributions (118 ) (118 ) Net income available to common unitholders - basic $ 52,643 150,216 $ 0.35 $ 50,826 149,534 $ 0.34 Dilutive units for long-term compensation plans — 820 — 740 Net income available to common unitholders - diluted $ 52,643 151,036 $ 0.35 $ 50,826 150,274 $ 0.34 For the Six Months Ended For the Six Months Ended June 30, 2017 June 30, 2016 Income (Numerator) Weighted Average Units (Denominator) Per Unit Income (Numerator) Weighted Average Units (Denominator) Per Unit Net income - net of noncontrolling interest - consolidated joint ventures $ 96,942 $ 110,007 Less: Preferred unit distributions (236 ) (236 ) Net income available to common unitholders - basic 96,706 150,130 $ 0.64 109,771 149,541 $ 0.73 Dilutive units for long-term compensation plans — 753 — 620 Net income available to common unitholders - diluted $ 96,706 150,883 $ 0.64 $ 109,771 150,161 $ 0.73

Accumulated Other Comprehensi29

Accumulated Other Comprehensive Income (Tables)	6 Months Ended
	Jun. 30, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]	The following table sets forth the components of Accumulated Other Comprehensive Loss (in thousands): As of and for the six months ended June 30, 2017 2016 Foreign Currency Translation: Beginning balance $ (56,767 ) $ (22,023 ) Translation adjustment 10,680 (18,596 ) Ending balance (46,087 ) (40,619 ) Derivative Instruments: Beginning balance (455 ) (865 ) Unrealized loss (41 ) (2,354 ) Reclassification adjustment (1) 316 559 Ending balance (180 ) (2,660 ) Total accumulated other comprehensive loss (46,267 ) (43,279 ) Less: portion included in noncontrolling interest – operating partnership 935 863 Total accumulated other comprehensive loss included in shareholders' equity/owners' equity $ (45,332 ) $ (42,416 ) (1) Amounts reclassified out of Accumulated Other Comprehensive Loss/General & Limited Partner's Equity into contractual interest expense.

Real Estate (Tables)

Real Estate (Tables)	6 Months Ended
	Jun. 30, 2017
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment [Table Text Block]	Information on the operating properties and land parcels the Company sold during the three and six months ended June 30, 2017 is as follows: Three Months Ended June 30, 2017 Six Months Ended June 30, 2017 Number of Buildings Acres of Developable Land Leaseable Square Feet Gross Proceeds (in thousands) Number of Buildings Acres of Developable Land Leaseable Square Feet Gross Proceeds (in thousands) Chicago/Minneapolis 1 — 31,116 $ 3,100 1 — 31,116 $ 3,100 Florida — 11 — 2,636 — 11 — 2,636 Houston — 7 — 1,995 — 7 — 1,995 Philadelphia — 2 — 6,904 — 2 — 6,904 Southeastern PA 1 3 62,386 6,975 2 3 95,413 9,050 Other — 6 — 3,739 — 6 — 3,739 2 29 93,502 $ 25,349 3 29 126,529 $ 27,424

Segment Information (Tables)

Segment Information (Tables)	6 Months Ended
	Jun. 30, 2017
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment, Revenue and Net Operating Income [Table Text Block]	The operating information by reportable segment is as follows (in thousands): Three Months Six Months Ended June 30, Ended June 30, 2017 2016 2017 2016 Operating revenue Carolinas/Richmond $ 18,225 $ 16,174 $ 36,282 $ 31,934 Chicago/Minneapolis 15,767 21,891 31,642 43,430 Florida 14,482 27,798 28,730 57,115 Houston 14,779 14,204 29,553 28,971 Lehigh/Central PA 39,815 33,782 81,350 68,025 Philadelphia 10,928 10,386 22,363 20,741 Southeastern PA 15,127 24,343 29,742 50,226 United Kingdom 3,262 3,525 6,431 7,077 Other 32,166 34,444 62,538 69,441 Segment-level operating revenue 164,551 186,547 328,631 376,960 Reconciliation to total operating revenues Development service fee income 18,259 — 29,744 — Other 320 107 121 (165 ) Total operating revenue $ 183,130 $ 186,654 $ 358,496 $ 376,795 SNOI Carolinas/Richmond $ 13,094 $ 11,219 $ 26,077 $ 22,059 Chicago/Minneapolis 10,011 11,872 19,360 23,243 Florida 10,003 16,741 19,510 34,788 Houston 7,761 8,036 14,562 16,869 Lehigh/Central PA 29,083 24,755 58,661 48,957 Philadelphia 8,475 7,981 17,234 15,339 Southeastern PA 8,507 14,549 16,619 28,300 United Kingdom 1,649 2,438 3,506 4,842 Other 21,935 22,953 42,191 45,779 SNOI 110,518 120,544 217,720 240,176 Reconciliation to net income Interest expense (21,942 ) (30,131 ) (44,285 ) (61,543 ) Depreciation/amortization expense (1) (33,115 ) (39,161 ) (66,308 ) (78,959 ) Gain on property dispositions 5,895 3,832 6,702 24,353 Equity in earnings of unconsolidated joint ventures 3,990 5,583 9,721 10,497 General and administrative expense (1) (11,047 ) (10,135 ) (23,301 ) (24,927 ) Income taxes (1) 104 (653 ) (176 ) (1,222 ) Other (1,585 ) 1,178 (3,011 ) 1,745 Net income $ 52,818 $ 51,057 $ 97,062 $ 110,120 (1) Excludes costs which are included in determining SNOI.
Assets by Segment and Reconciliation to Consolidated [Table Text Block]	The Company's total assets by reportable segment as of June 30, 2017 and December 31, 2016 is as follows (in thousands): June 30, 2017 December 31, 2016 Carolinas/Richmond $ 512,329 $ 503,920 Chicago/Minnesota 609,962 616,298 Florida 507,873 514,431 Houston 529,946 530,438 Lehigh/Central PA 1,350,454 1,311,815 Philadelphia 610,025 557,510 Southeastern PA 271,035 262,155 United Kingdom 227,793 189,766 Other 1,487,741 1,403,431 Segment-level total assets 6,107,158 5,889,764 Corporate Other 52,477 103,049 Total assets $ 6,159,635 $ 5,992,813

Noncontrolling Interest - Ope32

Noncontrolling Interest - Operating Partnership/Limited Partners' Equity - Preferred Units (Tables)	6 Months Ended
	Jun. 30, 2017
Temporary Equity [Line Items]
Schedule of Temporary Equity [Table Text Block]	As of June 30, 2017 , the Company had outstanding the following cumulative preferred units of the Operating Partnership: ISSUE AMOUNT UNITS LIQUIDATION PREFERENCE DIVIDEND RATE (in 000’s) Series I-2 $ 7,537 301 $25 6.25 %

Disclosure of Fair Value of F33

Disclosure of Fair Value of Financial Instruments (Tables)	6 Months Ended
	Jun. 30, 2017
Debt Instrument, Fair Value Disclosure [Abstract]
Fair Value, by Balance Sheet Grouping [Table Text Block]	The following summarizes the fair value of the Company's mortgage loans and unsecured notes as of December 31, 2016 and June 30, 2017 (in thousands): Mortgage Loans Unsecured Notes Carrying Value Fair Value Carrying Value Fair Value As of December 31, 2016 $ 276,650 $ 286,684 $ 2,280,286 $ 2,340,762 As of June 30, 2017 $ 271,851 $ 283,911 $ 2,281,650 $ 2,364,004

Derivative Instruments (Tables)

Derivative Instruments (Tables)	6 Months Ended
	Jun. 30, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments, Gain (Loss) [Table Text Block]	The following table presents the location in the financial statements of the gains or losses recognized related to the Company’s cash flow hedges for the three months ended June 30, 2017 and 2016 (in thousands): Three Months Ended Six Months Ended June 30, 2017 June 30, 2016 June 30, 2017 June 30, 2016 Amount of loss related to the effective portion recognized in other comprehensive loss $ (163 ) $ (700 ) $ (25 ) $ (2,343 ) Amount of loss related to the effective portion subsequently reclassified to interest expense $ (129 ) $ (276 ) $ (316 ) $ (559 ) Amount of (loss) gain related to the ineffective portion recognized in interest expense $ (9 ) $ (22 ) $ 14 $ (78 )

Commitments and Contingencies (

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Future Minimum Rental Payments	Future minimum rental payments under the terms of all non-cancelable operating ground leases under which the Company is the lessee, as of June 30, 2017 , were as follows (in thousands): Year Amount 2017 (remaining) $ 825 2018 1,754 2019 1,754 2020 1,754 2021 1,754 2022 and thereafter 34,872 Total $ 42,713

Supplemental Disclosure to St36

Supplemental Disclosure to Statements of Cash Flows (Tables)	6 Months Ended
	Jun. 30, 2017
Supplemental Cash Flow Information [Abstract]
Supplemental Disclosure to Statements of Cash Flows	The following are supplemental disclosures to the consolidated statements of cash flows for the six months ended June 30, 2017 and 2016 (amounts in thousands): 2017 2016 Write-off of fully depreciated/amortized property and deferred costs $ 19,833 $ 19,002 Write-off of depreciated/amortized property and deferred costs due to sale $ 8,989 $ 33,857 Redemption of noncontrolling interests - common units $ 27 $ — Unrealized gain (loss) on cash flow hedge $ 275 $ (1,795 ) Changes in accrued development capital expenditures $ 13,124 $ 2,383 Capitalized equity-based compensation $ 739 $ 808

Organization and Basis of Pre37

Organization and Basis of Presentation (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Ownership interest in operating partnership - Limited Partnership	97.70%
Liberty Comcast 1701 JFK Boulevard, LP [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage	20.00%
Liberty Comcast 1701 JFK Boulevard, LP [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Other Investments [Member]
Variable Interest Entity [Line Items]
Equity investment in joint venture	$ 17.7	$ 18.7
Maximum exposure to loss	$ 17.7	$ 18.7

Organization and Basis of Pre38

Organization and Basis of Presentation Prior period adjustments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Prior Period Adjustments [Line Items]
Cash outflow for shares related to tax withholdings			$ 4,668	$ 45,006
Development service fee expense	$ 17,828	$ 0	$ 28,832	0
Other Income [Member] | Scenario, Previously Reported [Member]
Prior Period Adjustments [Line Items]
Development service fee income		1,198		2,570
General and Administrative Expense [Member] | Scenario, Previously Reported [Member]
Prior Period Adjustments [Line Items]
Development service fee expense		$ 1,054		2,152
Accounting Standards Update 2016-09 [Member] | Scenario, Previously Reported [Member]
Prior Period Adjustments [Line Items]
Cash outflow for shares related to tax withholdings				$ 4,100

Income per Common Share of th39

Income per Common Share of the Trust (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income (Numerator) [Abstract]
Net income available to common shareholders	$ 51,411	$ 49,627	$ 94,443	$ 107,181
Weighted Average Shares (Denominator) [Abstract]
Weighted Average Number of Shares Outstanding, Basic	146,688	145,995	146,602	146,002
Dilutive shares for long-term compensation plans	820	740	753	620
Weighted Average Number of Shares Outstanding, Diluted	147,508	146,735	147,355	146,622
Common shares [Member]
Earnings Per Share, Basic [Abstract]
Income per common share - basic	$ 0.35	$ 0.34	$ 0.64	$ 0.73
Earnings Per Share, Diluted [Abstract]
Income per common share - diluted	$ 0.35	$ 0.34	$ 0.64	$ 0.73

Income per Common Share of th40

Income per Common Share of the Trust Income per Common Share of the Trust - Anti-dilutive Options (Details) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Stock Option [Member]
Antidilutive Options Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Options Excluded from Computation of Earnings Per Share	0	885,000	0	1,668,000

Income per Common Share of th41

Income per Common Share of the Trust - Options Exercised (Details) - shares	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Jun. 30, 2017	Dec. 31, 2016
Stock Option [Member] | Common shares [Member]
Stock Option Exercises [Line Items]
Amount of Options Exercises in Period	77,000	88,000	369,000

Income per Common Share of th42

Income per Common Share of the Trust - Share Repurchase (Details) - Common shares [Member] - 2015 Share Repurchase Program [Member] shares in Millions, $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2017USD ($)shares	Jun. 30, 2017USD ($)shares
Class of Stock [Line Items]
Authorized amount of shares available to be repurchased under a share repurchase plan | $	$ 250	$ 250
Number of shares repurchased during period | shares	0	0

Income per Common Unit of the43

Income per Common Unit of the Operating Partnership - Diluted (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income (Numerator) [Abstract]
Net income available to common shareholders	$ 51,411	$ 49,627	$ 94,443	$ 107,181
Weighted Average Units (Denominator) [Abstract]
Weighted Average Number of Shares Outstanding, Basic	146,688	145,995	146,602	146,002
Dilutive units for long-term compensation plans	820	740	753	620
Weighted Average Number of Shares Outstanding, Diluted	147,508	146,735	147,355	146,622
Liberty Property Limited Partnership [Member]
Income (Numerator) [Abstract]
Income from continuing operations net of noncontrolling interest - consolidated joint ventures	$ 52,761	$ 50,944	$ 96,942	$ 110,007
Less: Preferred unit distributions	(118)	(118)	(236)	(236)
Net income available to common shareholders	$ 52,643	$ 50,826	$ 96,706	$ 109,771
Weighted Average Units (Denominator) [Abstract]
Weighted Average Number of Shares Outstanding, Basic	150,216	149,534	150,130	149,541
Dilutive units for long-term compensation plans	820	740	753	620
Weighted Average Number of Shares Outstanding, Diluted	151,036	150,274	150,883	150,161
Liberty Property Limited Partnership [Member] | Common Units [Member]
Earnings Per Unit, Basic [Abstract]
Income per common share - basic	$ 0.35	$ 0.34	$ 0.64	$ 0.73
Earnings Per Unit, Diluted [Abstract]
Income per common share - diluted	$ 0.35	$ 0.34	$ 0.64	$ 0.73

Income per Common Unit of the44

Income per Common Unit of the Operating Partnership - Anti-dilutive Options (Details) - Stock Option [Member] - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Antidilutive Options Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Options Excluded from Computation of Earnings Per Share	0	885,000	0	1,668,000
Liberty Property Limited Partnership [Member]
Antidilutive Options Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Options Excluded from Computation of Earnings Per Share	0	885,000	0	1,668,000

Income per Common Unit of the45

Income per Common Unit of the Operations Partnership - Options Exercised (Details) - shares	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Jun. 30, 2017	Dec. 31, 2016
Liberty Property Limited Partnership [Member] | Stock Option [Member] | Common Units [Member]
Stock Option Exercises [Line Items]
Amount of Options Exercises in Period	77,000	88,000	369,000

Income per Common Unit of the46

Income per Common Unit of the Operating Partnership - Unit Repurchase (Details) - 2015 Share Repurchase Program [Member] $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2017USD ($)shares	Jun. 30, 2017USD ($)shares
Common shares [Member]
Class of Stock [Line Items]
Authorized amount of shares available to be repurchased under a share repurchase plan | $	$ 250	$ 250
Number of units repurchased during period | shares	0	0
Liberty Property Limited Partnership [Member] | Common Units [Member]
Class of Stock [Line Items]
Authorized amount of shares available to be repurchased under a share repurchase plan | $	$ 250	$ 250
Number of units repurchased during period | shares	0	0

Accumulated Other Comprehensi47

Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance		$ 3,062,923
Ending Balance		3,060,660
Total accumulated other comprehensive loss		3,062,923		$ 3,060,660	$ 3,062,923
Total accumulated other comprehensive loss included in shareholders' equity/owners' equity				3,001,589	3,003,391
Accumulated Foreign Currency Adjustment Including Portion Attributable to Noncontrolling Interest [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance		(56,767)	$ (22,023)
Unrealized income (loss)		10,680	(18,596)
Ending Balance		(46,087)	(40,619)
Total accumulated other comprehensive loss		(56,767)	(22,023)	(46,087)	(56,767)	$ (40,619)
Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance		(455)	(865)
Unrealized income (loss)		(41)	(2,354)
Reclassification adjustment	[1]	316	559
Ending Balance		(180)	(2,660)
Total accumulated other comprehensive loss		(455)	(865)	(180)	(455)	(2,660)
AOCI Including Portion Attributable to Noncontrolling Interest [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Ending Balance		(46,267)	(43,279)
Total accumulated other comprehensive loss		(46,267)	(43,279)	(46,267)		(43,279)
AOCI Attributable to Noncontrolling Interest [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Ending Balance		935	863
Total accumulated other comprehensive loss		935	$ 863	935		863
AOCI Attributable to Parent [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance		(56,031)
Ending Balance		(45,332)
Total accumulated other comprehensive loss		$ (56,031)		(45,332)	$ (56,031)
Total accumulated other comprehensive loss included in shareholders' equity/owners' equity				$ (45,332)		$ (42,416)
[1]	Amounts reclassified out of Accumulated Other Comprehensive Loss/General & Limited Partner's Equity into contractual interest expense.

Assets Held for Sale (Details)

Assets Held for Sale (Details) - Florida [Member] - 2017 held for sale [Member] - Disposal Group, Held-for-sale, Not Discontinued Operations [Member] $ in Millions	Jun. 30, 2017USD ($)a
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Acres of developable land | a	4.9
Land held for development | $	$ 2.7

Building Acquisitions and Dispo

Building Acquisitions and Dispositions (Details) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2017USD ($)ft²abldg	Jun. 30, 2017USD ($)ft²abldg	Jun. 30, 2016USD ($)
Property, Plant and Equipment [Line Items]
Proceeds from Sale of Buildings and Land		$ 26,220	$ 139,814
Disposal Group, Not Discontinued Operations [Member] | 2017 sales [Member] | Operating Segments [Member] | Land, Buildings and Improvements [Member]
Property, Plant and Equipment [Line Items]
Number of Real Estate Properties | bldg	3	3
Acres of developable land | a	29	29
Leaseable square feet | ft²	126,529	126,529
Proceeds from Sale of Buildings and Land		$ 27,424
Disposal Group, Not Discontinued Operations [Member] | 2017 sales [Member] | Operating Segments [Member] | Chicago Minneapolis [Member] | Land, Buildings and Improvements [Member]
Property, Plant and Equipment [Line Items]
Number of Real Estate Properties | bldg	1	1
Acres of developable land | a	0	0
Leaseable square feet | ft²	31,116	31,116
Proceeds from Sale of Buildings and Land		$ 3,100
Disposal Group, Not Discontinued Operations [Member] | 2017 sales [Member] | Operating Segments [Member] | Florida [Member] | Land, Buildings and Improvements [Member]
Property, Plant and Equipment [Line Items]
Number of Real Estate Properties | bldg	0	0
Acres of developable land | a	11	11
Leaseable square feet | ft²	0	0
Proceeds from Sale of Buildings and Land		$ 2,636
Disposal Group, Not Discontinued Operations [Member] | 2017 sales [Member] | Operating Segments [Member] | Houston [Member] | Land, Buildings and Improvements [Member]
Property, Plant and Equipment [Line Items]
Number of Real Estate Properties | bldg	0	0
Acres of developable land | a	7	7
Leaseable square feet | ft²	0	0
Proceeds from Sale of Buildings and Land		$ 1,995
Disposal Group, Not Discontinued Operations [Member] | 2017 sales [Member] | Operating Segments [Member] | Philadelphia [Member] | Land, Buildings and Improvements [Member]
Property, Plant and Equipment [Line Items]
Number of Real Estate Properties | bldg	0	0
Acres of developable land | a	2	2
Leaseable square feet | ft²	0	0
Proceeds from Sale of Buildings and Land		$ 6,904
Disposal Group, Not Discontinued Operations [Member] | 2017 sales [Member] | Operating Segments [Member] | Southeastern PA [Member] | Land, Buildings and Improvements [Member]
Property, Plant and Equipment [Line Items]
Number of Real Estate Properties | bldg	2	2
Acres of developable land | a	3	3
Leaseable square feet | ft²	95,413	95,413
Proceeds from Sale of Buildings and Land		$ 9,050
Disposal Group, Not Discontinued Operations [Member] | 2017 sales [Member] | Operating Segments [Member] | Other Segments [Member] | Land, Buildings and Improvements [Member]
Property, Plant and Equipment [Line Items]
Number of Real Estate Properties | bldg	0	0
Acres of developable land | a	6	6
Leaseable square feet | ft²	0	0
Proceeds from Sale of Buildings and Land		$ 3,739
Disposal Group, Not Discontinued Operations [Member] | 2017 sales current quarter [Member] | Operating Segments [Member] | Land, Buildings and Improvements [Member]
Property, Plant and Equipment [Line Items]
Number of Real Estate Properties | bldg	2	2
Acres of developable land | a	29	29
Leaseable square feet | ft²	93,502	93,502
Proceeds from Sale of Buildings and Land	$ 25,349
Disposal Group, Not Discontinued Operations [Member] | 2017 sales current quarter [Member] | Operating Segments [Member] | Chicago Minneapolis [Member] | Land, Buildings and Improvements [Member]
Property, Plant and Equipment [Line Items]
Number of Real Estate Properties | bldg	1	1
Acres of developable land | a	0	0
Leaseable square feet | ft²	31,116	31,116
Proceeds from Sale of Buildings and Land	$ 3,100
Disposal Group, Not Discontinued Operations [Member] | 2017 sales current quarter [Member] | Operating Segments [Member] | Florida [Member] | Land, Buildings and Improvements [Member]
Property, Plant and Equipment [Line Items]
Number of Real Estate Properties | bldg	0	0
Acres of developable land | a	11	11
Leaseable square feet | ft²	0	0
Proceeds from Sale of Buildings and Land	$ 2,636
Disposal Group, Not Discontinued Operations [Member] | 2017 sales current quarter [Member] | Operating Segments [Member] | Houston [Member] | Land, Buildings and Improvements [Member]
Property, Plant and Equipment [Line Items]
Number of Real Estate Properties | bldg	0	0
Acres of developable land | a	7	7
Leaseable square feet | ft²	0	0
Proceeds from Sale of Buildings and Land	$ 1,995
Disposal Group, Not Discontinued Operations [Member] | 2017 sales current quarter [Member] | Operating Segments [Member] | Philadelphia [Member] | Land, Buildings and Improvements [Member]
Property, Plant and Equipment [Line Items]
Number of Real Estate Properties | bldg	0	0
Acres of developable land | a	2	2
Leaseable square feet | ft²	0	0
Proceeds from Sale of Buildings and Land	$ 6,904
Disposal Group, Not Discontinued Operations [Member] | 2017 sales current quarter [Member] | Operating Segments [Member] | Southeastern PA [Member] | Land, Buildings and Improvements [Member]
Property, Plant and Equipment [Line Items]
Number of Real Estate Properties | bldg	1	1
Acres of developable land | a	3	3
Leaseable square feet | ft²	62,386	62,386
Proceeds from Sale of Buildings and Land	$ 6,975
Disposal Group, Not Discontinued Operations [Member] | 2017 sales current quarter [Member] | Operating Segments [Member] | Other Segments [Member] | Land, Buildings and Improvements [Member]
Property, Plant and Equipment [Line Items]
Number of Real Estate Properties | bldg	0	0
Acres of developable land | a	6	6
Leaseable square feet | ft²	0	0
Proceeds from Sale of Buildings and Land	$ 3,739
2017 acquisitions current quarter [Member] | Operating Segments [Member] | Southern California [Member]
Property, Plant and Equipment [Line Items]
Number of Real Estate Properties | bldg	1	1
Leaseable square feet | ft²	101,000	101,000
Purchase price	$ 19,100
2017 acquisitions [Member] | Operating Segments [Member] | Southern California [Member]
Property, Plant and Equipment [Line Items]
Number of Real Estate Properties | bldg	1	1
Leaseable square feet | ft²	101,000	101,000
Purchase price		$ 19,100

Segment Information - Income St

Segment Information - Income Statement (Details) - USD ($)		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Operating revenue		$ 183,130,000	$ 186,654,000	$ 358,496,000	$ 376,795,000
Net operating income		63,271,000	67,533,000	122,066,000	128,776,000
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Interest expense		(21,942,000)	(30,131,000)	(44,285,000)	(61,543,000)
Depreciation and amortization expense				(92,310,000)	(109,047,000)
Gain on property dispositions		5,895,000	3,832,000	6,702,000	24,353,000
Equity in earnings of unconsolidated joint ventures		3,990,000	5,583,000	9,721,000	10,497,000
General and administrative expense		(15,282,000)	(15,629,000)	(32,224,000)	(36,619,000)
Income taxes		(324,000)	(752,000)	(946,000)	(1,553,000)
Net income		52,818,000	51,057,000	97,062,000	110,120,000
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenue		0	0	0	0
Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenue		164,551,000	186,547,000	328,631,000	376,960,000
Net operating income		110,518,000	120,544,000	217,720,000	240,176,000
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Operating revenue		320,000	107,000	121,000	(165,000)
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Interest expense		(21,942,000)	(30,131,000)	(44,285,000)	(61,543,000)
Depreciation and amortization expense	[1]	(33,115,000)	(39,161,000)	(66,308,000)	(78,959,000)
Gain on property dispositions		5,895,000	3,832,000	6,702,000	24,353,000
Equity in earnings of unconsolidated joint ventures		3,990,000	5,583,000	9,721,000	10,497,000
General and administrative expense	[1]	(11,047,000)	(10,135,000)	(23,301,000)	(24,927,000)
Income taxes	[1]	104,000	(653,000)	(176,000)	(1,222,000)
Other		(1,585,000)	1,178,000	(3,011,000)	1,745,000
Development Service Fee Income [Member] | Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Operating revenue		18,259,000	0	29,744,000	0
Carolinas Richmond [Member] | Operating Segments [Member] | North America [Member]
Segment Reporting Information [Line Items]
Operating revenue		18,225,000	16,174,000	36,282,000	31,934,000
Net operating income		13,094,000	11,219,000	26,077,000	22,059,000
Chicago Minneapolis [Member] | Operating Segments [Member] | North America [Member]
Segment Reporting Information [Line Items]
Operating revenue		15,767,000	21,891,000	31,642,000	43,430,000
Net operating income		10,011,000	11,872,000	19,360,000	23,243,000
Florida [Member] | Operating Segments [Member] | North America [Member]
Segment Reporting Information [Line Items]
Operating revenue		14,482,000	27,798,000	28,730,000	57,115,000
Net operating income		10,003,000	16,741,000	19,510,000	34,788,000
Houston [Member] | Operating Segments [Member] | North America [Member]
Segment Reporting Information [Line Items]
Operating revenue		14,779,000	14,204,000	29,553,000	28,971,000
Net operating income		7,761,000	8,036,000	14,562,000	16,869,000
Lehigh Central PA [Member] | Operating Segments [Member] | North America [Member]
Segment Reporting Information [Line Items]
Operating revenue		39,815,000	33,782,000	81,350,000	68,025,000
Net operating income		29,083,000	24,755,000	58,661,000	48,957,000
Philadelphia [Member] | Operating Segments [Member] | North America [Member]
Segment Reporting Information [Line Items]
Operating revenue		10,928,000	10,386,000	22,363,000	20,741,000
Net operating income		8,475,000	7,981,000	17,234,000	15,339,000
Southeastern PA [Member] | Operating Segments [Member] | North America [Member]
Segment Reporting Information [Line Items]
Operating revenue		15,127,000	24,343,000	29,742,000	50,226,000
Net operating income		8,507,000	14,549,000	16,619,000	28,300,000
United Kingdom [Member] | Operating Segments [Member] | UNITED KINGDOM
Segment Reporting Information [Line Items]
Operating revenue		3,262,000	3,525,000	6,431,000	7,077,000
Net operating income		1,649,000	2,438,000	3,506,000	4,842,000
Other Segments [Member] | Operating Segments [Member] | North America [Member]
Segment Reporting Information [Line Items]
Operating revenue		32,166,000	34,444,000	62,538,000	69,441,000
Net operating income		$ 21,935,000	$ 22,953,000	$ 42,191,000	$ 45,779,000
[1]	Excludes costs which are included in determining SNOI.

Segment Information - Total Ass

Segment Information - Total Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Assets	$ 6,159,635	$ 5,992,813
Operating Segments [Member]
Segment Reporting Information [Line Items]
Assets	6,107,158	5,889,764
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Assets	52,477	103,049
North America [Member] | Operating Segments [Member] | Carolinas Richmond [Member]
Segment Reporting Information [Line Items]
Assets	512,329	503,920
North America [Member] | Operating Segments [Member] | Chicago Minneapolis [Member]
Segment Reporting Information [Line Items]
Assets	609,962	616,298
North America [Member] | Operating Segments [Member] | Florida [Member]
Segment Reporting Information [Line Items]
Assets	507,873	514,431
North America [Member] | Operating Segments [Member] | Houston [Member]
Segment Reporting Information [Line Items]
Assets	529,946	530,438
North America [Member] | Operating Segments [Member] | Lehigh Central PA [Member]
Segment Reporting Information [Line Items]
Assets	1,350,454	1,311,815
North America [Member] | Operating Segments [Member] | Philadelphia [Member]
Segment Reporting Information [Line Items]
Assets	610,025	557,510
North America [Member] | Operating Segments [Member] | Southeastern PA [Member]
Segment Reporting Information [Line Items]
Assets	271,035	262,155
North America [Member] | Operating Segments [Member] | Other Segments [Member]
Segment Reporting Information [Line Items]
Assets	1,487,741	1,403,431
UNITED KINGDOM | Operating Segments [Member] | United Kingdom [Member]
Segment Reporting Information [Line Items]
Assets	$ 227,793	$ 189,766

Accounting for the Impairment52

Accounting for the Impairment of Long-Lived Assets and Fee Development Contracts (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Property, Plant and Equipment [Line Items]
Impairment - real estate assets	$ 0	$ 0	$ 0	$ 0
Loss on fee development contracts	$ 0	$ 0	$ 0	$ 0

Noncontrolling Interests of t53

Noncontrolling Interests of the Trust- Narrative (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Redeemable Noncontrolling Interest [Line Items]
Limited Partners' common units outstanding	3,528,281	3,530,031
Market value of common units based on closing price	$ 143.6
Liberty Property Limited Partnership [Member]
Redeemable Noncontrolling Interest [Line Items]
Limited Partners' common units outstanding	3,528,281	3,530,031

Limited Partners' Equity of t54

Limited Partners' Equity of the Operating Partnership - Narrative (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Limited Partners' Capital Account [Line Items]
Limited Partners' common units outstanding	3,528,281	3,530,031
Liberty Property Limited Partnership [Member]
Limited Partners' Capital Account [Line Items]
Limited Partners' common units outstanding	3,528,281	3,530,031
market value of the outstanding common units	$ 143.6

Noncontrolling Interest - Ope55

Noncontrolling Interest - Operating Partnership/Limited Partners' Equity - Preferred Units (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Temporary Equity [Line Items]
Noncontrolling interest - operating partnership - 301,483 preferred units outstanding as of June 30, 2017 and December 31, 2016	$ 7,537	$ 7,537
Series I 2 [Member]
Temporary Equity [Line Items]
Noncontrolling interest - operating partnership - 301,483 preferred units outstanding as of June 30, 2017 and December 31, 2016	$ 7,537
Units	301,483	301,483
Liquidation Preference	$ 25
Dividend Rate	6.25%

Disclosure of Fair Value of F56

Disclosure of Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mortgage loans	$ 271,851	$ 276,650
Unsecured Debt	2,281,650	2,280,286
Unsecured Debt [Member] | Fair Value, Inputs, Level 3 [Member] | Long-term Debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of debt	2,364,004	2,340,762
Mortgage Loans | Fair Value, Inputs, Level 3 [Member] | Long-term Debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of debt	$ 283,911	$ 286,684

Unconsolidated Joint Ventures (

Unconsolidated Joint Ventures (Details) - Cambridge Medipark Ltd [Member] - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	50.00%		50.00%
Joint venture, 2017 sales current quarter [Member] | Gain on equity method investments [Member] | Disposal Group, Not Discontinued Operations [Member] | Leaseholds and Leasehold Improvements [Member]
Schedule of Equity Method Investments [Line Items]
Gain (loss) on sale of leasehold interests	$ 1,500,000
Joint venture, 2017 sales [Member] | Gain on equity method investments [Member] | Disposal Group, Not Discontinued Operations [Member] | Leaseholds and Leasehold Improvements [Member]
Schedule of Equity Method Investments [Line Items]
Gain (loss) on sale of leasehold interests			$ 4,500,000
Joint venture, 2016 sales current quarter [Member] | Gain on equity method investments [Member] | Disposal Group, Not Discontinued Operations [Member] | Leaseholds and Leasehold Improvements [Member]
Schedule of Equity Method Investments [Line Items]
Gain (loss) on sale of leasehold interests		$ 312,000
Joint venture, 2016 sales [Member] | Gain on equity method investments [Member] | Disposal Group, Not Discontinued Operations [Member] | Leaseholds and Leasehold Improvements [Member]
Schedule of Equity Method Investments [Line Items]
Gain (loss) on sale of leasehold interests				$ 206,000

Derivative Instruments (Details

Derivative Instruments (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017USD ($)	Jun. 30, 2016USD ($)	Jun. 30, 2017USD ($)	Jun. 30, 2016USD ($)	Dec. 31, 2016USD ($)
Interest Rate Derivatives [Abstract]
Number of interest rate swap contracts	3		3
aggregate notional amount	$ 97,600		$ 97,600		$ 98,900
Termination value of interest rate swap, including accrued interest	3,700		3,700
Interest Rate Cash Flow Hedges [Abstract]
Fair value of interest rate swaps	3,700		3,700		$ 4,900
Amount estimated to be reclassified from accumulated other comprehensive income as an increase to interest expense	200		200
Interest Rate Swap [Member] | Other Comprehensive Income (Loss) [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of loss related to the effective portion recognized in other comprehensive loss	(163)	$ (700)	(25)	$ (2,343)
Interest Rate Swap [Member] | Interest Expense [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of loss related to the effective portion subsequently reclassified to interest expense	(129)	(276)	(316)	(559)
Amount of (loss) gain related to the ineffective portion recognized in interest expense	$ (9)	$ (22)	$ 14	$ (78)

Commitments and Contingencies -

Commitments and Contingencies - Future Minimum Rental Payments (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Commitments and Contingencies Disclosure [Abstract]
2017 (remaining)	$ 825,000		$ 825,000
2,018	1,754,000		1,754,000
2,019	1,754,000		1,754,000
2,020	1,754,000		1,754,000
2,021	1,754,000		1,754,000
2022 and thereafter	34,872,000		34,872,000
Total	42,713,000		42,713,000
Other Expenses [Abstract]
Operating ground lease expense	$ 311,000	$ 237,000	$ 623,000	$ 493,000

Commitments and Contingencies60

Commitments and Contingencies - Loss Contingencies (Details) $ in Millions	Jun. 30, 2017USD ($)
Legal Matters [Abstract]
Loss Contingency, Pending Claims, Number	0
Other [Abstract]
Letter of credit obligations	$ 7.7

Commitments and Contingencies61

Commitments and Contingencies - Supply Commitments (Details) $ in Thousands, ft² in Millions	6 Months Ended
	Jun. 30, 2017USD ($)ft²bldgproperties	Dec. 31, 2016USD ($)
Supply Commitment [Line Items]
Development in progress	$ 410,027	$ 267,450
Supply Commitment [Member] | Construction in Progress [Member]
Supply Commitment [Line Items]
Deferred leasing costs in development	15,400
Remaining amount committed or obligated to pay	$ 11,800
Construction in Progress [Member]
Supply Commitment [Line Items]
Leaseable square feet | ft²	6.6
Number of Real Estate Properties | properties	27
Total anticipated development cost	$ 634,000
Buildings and land parcels [Member]
Supply Commitment [Line Items]
Remaining amount committed or obligated to pay	18,600
Tenant Improvements [Member]
Supply Commitment [Line Items]
Tenant improvements not yet completed	$ 21,100
Equity Method Investments [Member] | Supply Commitment [Member] | Construction in Progress [Member]
Supply Commitment [Line Items]
Number of Real Estate Properties | bldg	3
Remaining amount committed or obligated to pay	$ 966,700
American Water Works, Inc [Member] | Building and Building Improvements [Member]
Supply Commitment [Line Items]
Fee development commitment	170,100
Costs incurred to date	$ 46,700

Commitments and Contingencies62

Commitments and Contingencies - Purchase Commitments (Details) $ in Millions	Jun. 30, 2017USD ($)
Land and Land Improvements [Member] | Land Purchases [Member]
Long-term Purchase Commitment [Line Items]
Remaining amount committed to future acquisitions	$ 19.4

Supplemental Disclosure to St63

Supplemental Disclosure to Statements of Cash Flows (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Supplemental Cash Flow Information [Abstract]
Write-off of fully depreciated/amortized property and deferred costs	$ 19,833	$ 19,002
Write-off of depreciated/amortized property and deferred costs due to sale	8,989	33,857
Redemption of noncontrolling interests - common units	27	0
Unrealized gain (loss) on cash flow hedge	275	(1,795)
Changes in accrued development capital expenditures	13,124	2,383
Capitalized equity-based compensation	$ 739	$ 808

Subsequent Events (Details)

Subsequent Events (Details) $ in Thousands, ft² in Millions	Jul. 01, 2017USD ($)	Jul. 27, 2017USD ($)ft²abldg	Jun. 30, 2017USD ($)	Jun. 30, 2016USD ($)	Jun. 30, 2017USD ($)	Jun. 30, 2016USD ($)
Subsequent Event [Line Items]
Proceeds from Sale of Buildings and Land					$ 26,220	$ 139,814
Gain on property dispositions			$ 5,895	$ 3,832	6,702	$ 24,353
2015 sales [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Gain on property dispositions	$ 14,300
Other Liabilities [Member] | 2015 sales [Member]
Subsequent Event [Line Items]
Deferred Gain on Sale of Property			$ 14,300		$ 14,300
Lehigh Central PA [Member] | Disposal, Exercised Purchase Option [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Number of Real Estate Properties | bldg		2
square feet | ft²		1.7
Acres of developable land | a		44
Proceeds from Sale of Buildings and Land		$ 249,000
Lehigh Central PA [Member] | Minimum [Member] | Disposal, Exercised Purchase Option [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Gain on property dispositions		65,000
Lehigh Central PA [Member] | Maximum [Member] | Disposal, Exercised Purchase Option [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Gain on property dispositions		$ 70,000